THE STAR FORMATION NEWSLETTER · 2013-06-08 · The Star Formation Newsletter is a vehicle for ......

THE STAR FORMATION NEWSLETTERAn electronic publication dedicated to early stellar/planetary evolution and molecular clouds

No. 246 — 7 June 2013 Editor: Bo Reipurth ([email protected])

The Star Formation Newsletter

Editor: Bo [email protected]

Technical Editor: Eli [email protected]

Technical Assistant: Hsi-Wei [email protected]

Editorial Board

Joao AlvesAlan Boss

Jerome BouvierLee Hartmann

Thomas HenningPaul Ho

Jes JorgensenCharles J. Lada

Thijs KouwenhovenMichael R. MeyerRalph Pudritz

Luis Felipe RodrıguezEwine van Dishoeck

Hans Zinnecker

The Star Formation Newsletter is a vehicle forfast distribution of information of interest for as-tronomers working on star and planet formationand molecular clouds. You can submit materialfor the following sections: Abstracts of recently

accepted papers (only for papers sent to refereedjournals), Abstracts of recently accepted major re-

views (not standard conference contributions), Dis-

sertation Abstracts (presenting abstracts of newPh.D dissertations), Meetings (announcing meet-ings broadly of interest to the star and planet for-mation and early solar system community), New

Jobs (advertising jobs specifically aimed towardspersons within the areas of the Newsletter), andShort Announcements (where you can inform or re-quest information from the community). Addition-ally, the Newsletter brings short overview articleson objects of special interest, physical processes ortheoretical results, the early solar system, as wellas occasional interviews.

Newsletter Archivewww.ifa.hawaii.edu/users/reipurth/newsletter.htm

List of Contents

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

My Favorite Object . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Abstracts of Newly Accepted Papers . . . . . . . . . . 14

Abstracts of Newly Accepted Major Reviews . 51

Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 53

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Short Announcements . . . . . . . . . . . . . . . . . . . . . . . . 58

Cover Picture

NGC 7822 is an HII region, also known as Sharp-less 171, and located in Cepheus at the relativelyclose distance of 800 - 1000 pc. The central clusteris known as Berkeley 59. Parts of the complex areas young as 1-2 million years. The dominant ultra-violet source is the O5V star BD+66◦1673, whichis an eclipsing binary.

Image courtesy Martin Pugh.

Submitting your abstracts

Latex macros for submitting abstractsand dissertation abstracts (by e-mail [email protected]) are appended toeach Call for Abstracts. You can alsosubmit via the Newsletter web inter-face at http://www2.ifa.hawaii.edu/star-formation/index.cfm

2

Hans Zinneckerin conversation with Bo Reipurth

Q: Hans, we have known each other for a long time, 30

years, since the Les Houches school ”Birth and Infancy

of Stars”. How influential was that two week school in

August 1983 in the French Alps?

A: Very influential for many of us, myself included. Itwas there that long-term friendships among many youngastronomers were initiated. I vividly remember meet-ing John Bally, you Bo, Bruce Elmegreen, Gareth Wynn-Williams, Harold Yorke, to name but a few. Many of themfor the first time. This was the time when molecular out-flows were first discovered, as well as the proper motionsof Herbig-Haro objects, and I particularly recall discus-sions with George Herbig. It was also the time when thefirst results from the IRAS satellite began to appear, andduring the time of the school Bart Bok died in Tucson,AZ, making us feel that a baton was passed to the younggeneration.

Q: You presented your thesis work, a theoretical model of

the log-normal IMF in Les Houches, didn’t you?

A: Yes indeed. I gave a presentation on star formation as arandom multiplicative process. The idea was that severalfactors determine the critical protostellar mass, such astemperature, density, magnetic flux, angular momentum,geometry, etc in a multiplicative fashion. By and largethis model is still valid (Fred Adams introduced outflowsin 1996) and Basu and Jones (2004) as well as Phil Myers(2011) realized how to turn the high-mass lognormal tailinto a (Salpeter) power-law slope by adding the idea thatthe accretion time is uniformly distributed. Perhaps myown contribution here was to realize that for a log-normalIMF that turns down below a certain characteristic mass,the predicted number of brown dwarfs (or black dwarfs asthese objects were then called) is small, i.e. the numbersdo not diverge towards small masses, as an extrapolatedSalpeter low-mass IMF would imply.

Q: Didn’t you also develop and coin the term ”competitive

accretion” as a theoretical model for the IMF?

A: I guess this is correct. In my 1981 thesis I did two mod-els of the IMF, the log-normal model (originally based onthe concept of hierarchical fragmentation) and a power-law model (based on nonlinear Bondi-type gravitationalaccretion onto seed stars which were accreting from a lim-ited protocluster gas reservoir, hence the competition forgas accretion). This latter model was published in 1982 inthe Proc. of the Henry Draper Symposium on the OrionNebula and was popularized by Richard Larson who kindlyquoted my work. Had it not been for Richard, no-onemight have taken notice of that model. Now it is one ofmy most cited papers. Thank you, Richard.

Q: You were a theorist at heart, how come you turned into

a quasi-observational astronomer?

A: Yes, I started as a theorist, influenced by Prof. Kip-penhahn, and also by talking to Profs Bodenheimer andTscharnuter. Mind you, before my PhD in astrophysics Igot a diploma in physics in conformal quantum field the-ory - if anybody in astronomy knows what that is. Afterlooking around, I ended up for my thesis work in a group offar-infrared astronomers (balloon observations) at MPE inGarching, headed by Dr. Drapatz (my PhD thesis advisorwho taught me back-of-the envelope calculations). Thatenvironment helped me to get a sense for observations andthat the best astronomy is often done in interaction be-tween theory and observations.

Q: You did your postdoc years at the Royal Observatory

Edinburgh. How did that happen?

A: Interesting story. Coincidences. After my PhD I took atrip to Hawaii and managed to force my way up to UKIRTon Mauna Kea (ask Eric Becklin about that particularfacet). At Hale Pohaku (the dormitory halfway up themountain, quite rudimentary in 1981) I happened to meetGerry Gilmore (then at ROE) and gave him a copy of mythesis (in German). Next thing I hear, after being backin Garching, was that Malcolm Longair (then director atROE) who was visiting ESO Garching for a colloquium,had asked my advisor to see him before his departure.Indeed I met with Malcolm and he offered me to come toROE as a postdoc, on the basis of a mixed Royal Societyand German Science Foundation fellowship. I stayed foralmost 4 years. This was a crucial move to turn me fromtheory to observations.

Q: Can you elaborate a little more?

A:. I try. At ROE, I met Tom Geballe with whom I didmy first observing proposal (Brackett alpha in the OrionNebula), Mark McCaughrean and John Rayner, both PhDstudents of Dr. Ian McLean, as well as Colin Aspin, MikeBurton, Ron Garden, and others. This reads like a who iswho in infrared arrays at the time (Ian McLean heading

3

the IR-CAM development). I also there met Eric Becklin(on sabbatical) and Steve Beckwith (colloquium speaker),who alerted me to high angular resolution observations(lunar occultations and infrared speckle interferometry, re-spectively). Which I later applied to studies of pre-MainSequence binaries (originally with Chelli and Perrier 1986at ESO Chile and later with Leinert and Haas 1990 atCalar Alto). This exposure to infrared technology led to20 or so visits to Mauna Kea during my stay at ROE,which helped anchor my connection to observational as-tronomy.

Q: Apropos binaries. How did you get interested in pre-

MS binaries?

A: When I arrived in Edinburgh in August 1983, I had justcome back from an IAU Colloquium on binarity and a totalsolar eclipse in Indonesia. I had to write a report for theGerman funding agency. This developed into a review onbinary statistics and star formation. Binary star formation(mass ratios) clearly was the next logical step, after deal-ing with the possible origin of stellar masses. Everythingin those days was kind of pristine territory in the youngfield of star formation. One could still read all the papersever written on the subject. As an aside, it may be worthmentioning that it took a discussion with a young womanfrom India (her name was Jitinder, a student at ROE) whoinsisted and convinced me to confront/test my fledglingtheories with detailed infrared observations. Why don’tyou? she asked, and so I succumbed and changed my re-search into a more observational direction. ROE was theperfect place for me to do this.

Q: I remember a visit to ROE which hosted the Australian

Schmidt telescope plate library in which I was interested.

On that visit the two of us had an important encounter.

Would you like to tell the story?

A: Well, I was working away, but you said why don’t youtake a break and come for a weekend walk in the High-lands. Eventually I gave in to your persuasion. We hikedto a place called Arrochar near Glasgow and Loch Lomondand kept walking until we finally reached the end of thetrack. There was a wooden bench waiting for us and in-scribed in it was the thoughtful phrase: REST and BETHANKFUL. Something to remember. We had a longtalk, and our ensuing (pre-internet) scientific interactionculminated in your invitation to spend three months asan ESO senior visitor at La Silla in 1991 to carry outour plan of a CCD visual binary survey among southernpre-Main Sequence stars with the NTT. We did it, andduring that time I also was able to start learning Spanish(at lunch). As you know I love languages, and learningSpanish had a big influence later in my life. When ourpaper was published in Nov 1993, two other independentbut similar pre-Main Sequence binary surveys were pub-lished in the very same month (Leinert et al. where I was

a co-author and Ghez et al.). This was a great month forme and in fact for young binary star research.

Q:: In 1994, you discovered the beautiful HH212 molecular

hydrogen jet. How did this discovery come about?

A: Another interesting story which incidentally is con-nected to my deep interest in binary protostars. In 1987,in the early days of IR-arrays, I was interested in near-infrared imaging of cold, low-luminosity IRAS sources,in the hope to discover double stars in the same cloudcore, indicative of their joint formation (which was notyet proven at the time). IRAS 05413-0104 in Orion Bindeed showed two K-band near-infrared embedded pointsources, about 7 arcsec (300 AU) apart. Nothing hap-pened until 7 years later, when persistence paid off. Mycolleagues Mark McCaughrean and John Rayner (withme as a co-investigator) were observing the Orion Neb-ula Cluster with a new and better infrared array at theIRTF on Mauna Kea. Mark ran into a software problemrelated to the programming of the array mosaic patternand said: ”I need to fix this. You can have the telescopefor the next 10 min”. Well, intuition told me to have an-other look at that promising IRAS source with the near-infrared double star. So we changed target and took ashort integration. Upon inspecting the image, it seemedthe double star had become a quadruple system with allthe components aligned. Another deeper image resultedin an aligned system of 6 components. Wow. It was thenthat we realized that this could be a series of knots in amolecular hydrogen jet, as the H2 vibrational emission at2.12 micron fell into the K-band filter. We then switchedto the narrow-band 2.12 micron filter, and after a minuteor so, boom, the full highly bi-symmetric knotty jet inall its glory was revealed! By the way, the HH number(212) you gave the jet reflects the wavelength of its dis-covery. This serendipitous discovery was clearly my mostexciting observational experience (and perhaps my mostlasting legacy)!

Q:Which scientific question fascinates you most these days?

A: I would say: the formation of massive stars, in par-ticular the origin of the many close spectroscopic binarysystems among them. With orbital periods of a few days,separations of the order of 1 AU, and orbital speeds ofa few hundred km/s, these massive binaries challenge ourimagination. Some of these close binaries may even merge,to form very rapidly rotating single very massive O-stars.Maybe the progenitors of super-energetic long-durationgamma-ray bursts are related to massive binary star merg-ers or massive star collisions in dense clusters. In any case,the prevalence of these tight systems implies that binaryinteractions are the rule rather than the exception in mas-sive stellar evolution, something that many astrophysicistshave not fully realized.

4

Q: Why did you decide to join the SOFIA Airborne Ob-

servatory?

A: I suppose I was looking for a new challenge. For 15years I was the head of the star formation group at AIPPotsdam and I think we had a good group of about tenoutstanding scientists and hence we had an unusally stim-ulating work environment. We were the coordinating nodeof the European Commission Research Training Networkon the Formation and Evolution of Young Stellar Clusters(2001-2004) and the founding partner of another EU Re-search Training Network ”Constellation” on the origin ofstellar masses (2006-2010). Mark McCaughrean was thedriving force and the interaction with him and his vast ob-servational and managerial experience provided an excit-ing framework and much fun for many years at AIP. RalfKlessen added the theoretical star formation and simula-tion component and thus our group had all the necessaryelements of strong interaction of theory and observations.When McCaughrean and Klessen moved on to higher po-sitions (ESA, ITA) I felt I was too old writing grant pro-posals to rebuild the group. Then the SOFIA opportunitycame along. Germany, with a 20 percent share in this bigbilateral project (80 percent US, i.e. NASA), was look-ing for a German representative and deputy director. Iapplied, not least because Eric Becklin (SOFIA chief sci-entist) overwhelmingly encouraged me to do so. I got thejob and 3 years ago moved to California, to NASA-Ameswhere the SOFIA science center is located.

Q: How are you doing at SOFIA?

A: Working at SOFIA has been a challenge from the be-ginning, not only because I had to learn so much aboutmanagement of science and mission operations, but alsobecause scientifically I had to switch from being mainly anear-infrared stellar astronomer to becoming a far-infraredinterstellar astronomer. What I like about SOFIA is thebroad wavelength coverage (from optical to far-infrared)with the potential of major discoveries over its projected20 year lifetime. SOFIA is working almost routinely now,and flying on SOFIA is a unique and cool experience. Ihave flown 4 times so far. After Herschel ran out of cryo-gen, SOFIA is the only far-infrared facility for many yearsto come. Ending my career with SOFIA, and consider-ing my small beginnings in the far-infrared group at MPEGarching in 1977, I feel I have come full circle, a verysatisfactory emotion some 35 years later.

Q: You have also worked extensively with X-ray data, right?

A: Yes, I turned from infrared to X-rays in 1990 becauseROSAT, the X-ray satellite built at MPE, was launchedand, working at MPE, it would have been foolish to ignoreit. My interest in X-rays soon brought me to the Univ. ofWurzburg in Germany (where X-rays were discovered in1895 by C.W. Rontgen). I enjoyed my time at the univer-sity working with bright young people there (notably Wolf-gang Brandner and Thomas Preibisch) and with my men-tor Harold Yorke, to whom I also owe much, as he saved mefrom ”extinction” when I was unable to get a permanentjob at age 40. Before leaving Wurzburg for a permanentjob in Potsdam (at age 45), I initiated and co-organizedthe X-ray centenary conference ”Rontgenstrahlung fromthe Universe” in Wurzburg in 1995. (My multi-lambdabackground, infrared and X-rays, earned me the job).

Q: That was just one of the several conferences and sym-

posia that you initiated. Which were the others?

A: Well, in Potsdam I launched the IAU Symposium ”TheFormation of Binary Stars”. I fought hard to get thememorable number IAUS 200 in the year 2000 for this bi-nary conference. Later, in 2004, I launched another majorconference in Tuscany/Italy ”50 years of the Initial MassFunction” in honor of Ed Salpeter who wrote his seminalIMF paper in 1954 (published in 1955). I am now plan-ning a first SOFIA science symposium in the Bay Area forthe summer of 2014 (just before the Brazil soccer worldcup for which I want to travel to Brazil. I love soccer, Iplayed myself in my younger years in Bavaria, and I lovethe Brazilian people).

Q:You have been to more conferences than any other as-

tronomer that I know, and you have a large collection of

photos from these meetings. Do you plan to make this

photo archive public?

A: Indeed I probably have the biggest set of private pic-tures of astronomers. My plan is to work on these andmake them available after I formally retire in 3.5 years.

5

My Favorite ObjectIRAS 16293-2422

Luis Zapata

1 A Very Young Stellar Object

One of the consequences of the formation of a star isthe ”inside-out” collapse of dense parts of the molecu-lar clouds. This evolutionary phase is characterized bya central protostar and disk within an infalling envelopeof dust and gas. The infalling material passes through anaccretion disk, and then to the protostar allowing it togrow (Shu, Adams, and Lizano 1987). One of the veryfirst observational evidences of such infalling phenomenacame surprisingly from the young protostar IRAS16293-2422 (or L1689N) in the 80’s, almost in the same yearthat the famous Shu et al. review paper on star forma-tion was published. Figure 1 shows with a red box theposition of IRAS 16293 in the Rho Ophiuchi molecularcloud, one can see how this object is very embedded inits molecular natal cloud. The evidence for infall towardsIRAS16293 was based on a detailed analysis of the J=5-4 and 2-1 transitions of CS (Walker et al. 1986). Bothtransitions showed strong prominent self-absorption fea-tures superposed on a broader emission from an opticallythick molecular line. However, later Menten et al. (1987)using higher angular resolution CS J=3-2 and other linemaps argued that the kinematics of the CS gas might bebetter interpreted as rotation or outflow motions ratherthan infall. Recently, (sub)millimeter molecular line emis-sion maps obtained with ALMA have confirmed a directdetection of infall on the compact sources associated withIRAS16293. These studies for the first time have revealedstrong inverse P-Cygni profiles towards one source asso-ciated with IRAS16293 (Pineda et al 2012; Zapata et al.2013). In Figure 2 is shown the resolved infall motionstoward this component mapped at 690 GHz.

IRAS 16293 is an extremely cold far-infrared source lo-

Figure 1: Optical image of part of the Rho Ophiuchimolecular cloud and its vicinities. The yellowish star isAntares, and the M4 star cluster is to the right of Antares.The location of IRAS 16293-2422 is marked with a red box.This object is very embedded in its natal molecular cloudas one can be seen in this image. Image courtesy by TomO’Donoghue.

cated in the Rho Ophiuchi molecular cloud, one of theclosest places of recent star formation (located at a dis-tance of 120 pc; Loinard et al. 2008, Knude & Hog 1998).IRAS 16293 was first detected by the Infrared Astronomi-cal Satellite (IRAS) space-based observatory in the 25, 60,and 100 µm bands, this source is unresolved in all bands.The lack of detectable emission in the 12 µm band indi-cates that the source is a very cold dusty object.

Using the IRAS fluxes and a new data point at 2.7 mm ob-tained with the Owens Valley Radio Observatory (OVRO),Mundy et al. (1986) estimated a bolometric luminosityand a dust temperature of 27 L⊙ and 40 K for IRAS 16293,respectively. They confirmed that indeed this object isvery cold and is associated with a young low-mass proto-star. Such luminosity is in agreement with that value of23 L⊙ obtained by Walker et al. (1986), and the valueobtained recently by Correia et al. (2004) of 25 L⊙ (cor-rected with a more recent value of the distance).

6

Figure 2: Upper: ALMA H13CN (blue), HC15N(magenta), and CH3OH (green) spectra from IRAS16293−2422B. The black dashed line marks the systemicLSR velocity of IRAS 16293−2422B (VLSR ∼ 3 km s−1).

The observations made by Mundy et al. (1986) togetherwith subsequent high angular resolution observations (e.g.Wootten 1989) showed that IRAS16293 is really a binarysource separated by about 5′′. Moreover, the Very largeArray (VLA) centimeter observations fromWootten (1989)and Loinard et al. (2002) revealed that one component ofthe binary system, IRAS 16293A, splits up into a secondbinary system separated by only 50 AU. This binary sys-tem can be seen at resolutions better than about 0.2′′.These sources were named A1 and A2. The relative ori-entation of the A1/A2 pair at the time of its discoverywas very similar to the direction of the NE-SW flow, andA1 was initially believed to be an ejecta from A2. How-ever, analysis of the relative motion of A1 and A2 favorsa scenario where these two sources trace two stars in a bi-nary system (Loinard 2002; Chandler et al. 2005; Loinardet al. 2007; Pech et al. 2010). The other componentB remains single even at the highest angular resolutionavailable (∼ 0.05′′; Chandler et al. 2005; Rodrıguez etal. 2005). Subarcsecond submillimeter continuum ob-servations obtained with the Submillimeter Array (SMA)revealed additional structure in component A called Ab(Chandler et al. 2005). This source has not been detectedat any other wavelengths so far, and its exact nature re-mains poorly understood.

Mundy et al. (1992) suggested that the southeastern sourceIRAS 16293A contains only ∼ 0.5 M⊙ of dust and gas in a

Figure 3: SMA integrated blueshifted (blue contours) andredshifted (red contours) CO J=2-1 map of the outflowsfrom IRAS 16293-2422. Image taken from Yeh et al.(2008). The black circles represent the FWHM of theSMA. The crosses denote the positions of the two con-tinuum sources. Positions of the two prominent compactcomponents are labeled (b1 and b2). The filled ellipseindicates the synthesized beam size.

region of about 4′′ and its associated centimeter emissionis most likely produced by an ionized stellar wind as dis-cussed by Wootten (1989). On the other hand, the north-western source IRAS 16293B, displays continuum emissionwhich increases as ν2 throughout millimeter and centime-ter wavelengths (Estalella et al. 1991). This unique spec-trum can be explained if most of the continuum emissionis arising from dust. Subsequent observations made byRodrıguez et al. (2005) and Chandler et al. (2005) showthat IRAS 16293B has a spectral energy index of ν2.0−2.6

and a size of only 25 AU.

2 Outflows

Among the first works to detect outflows associated withIRAS 16293-2422 were those of Wootten et al. (1987) andMizuno et al. (1990). The multiple CO observations fromthese two studies revealed that the high velocity gas is re-solved into four compact separate lobes, consisting of twopairs of bipolar lobes, in addition to an extended monopo-lar blueshifted lobe. The quadrupolar outflow associatedto this source is oriented with one bipolar flow almosteast(blueshifted)-west(redshifted) (at a position angle of∼ 55◦), and the second one with its axis with an orienta-

7

Figure 4: Comparison between five radio images of IRAS16293A at different epochs. Note how the morphology ofcomponent A2 changes with time, while the other (A1)remains the same. Image taken from Pech et al. (2008).

tion northeast(redshifted)-southwest(blueshifted) or at aposition angle ∼ 110◦. Both flows seem to emanate fromIRAS 16293-2422A and B. A SMA map of compact COemission obtained by Yeh et al. (2008) is presented in Fig-ure 3. In this Figure one can clearly see the multiple east-west outflows emanating from this complex region. Someof these CO lobes coincide very well with SiO emission,a typical outflow tracer (Hirano et al. 2001). To explainthe conspicuous quadrupolar morphology of this outflowsystem, Walker et al. (1993) proposed that the two pairsof lobes correspond to two independent bipolar outflowsdriven by two independent sources. On the other hand,Mizuno et al. (1990) showed that the outflow is dynam-ically interacting with the dense ambient gas clump andsuggested that a single outflow lobe could be split into twolobes by the interaction. More recent observations fromStark et al. (2004) proposed that the northeast-southwestflow is powered by I16293A, while the east-west fossil flow

Figure 5: ALMA Integrated intensity of the weighted ve-locity (moment 1) colour map of the CO(6-5) emissionfrom source B overlaid in contours with the 0.45 mm con-tinuum emission (black thick line) and the velocity scaleof CO(6-5) (grey thin line). Image taken from Loinard etal. (2012).

was ejected from I16293B long time ago. In addition, theymentioned that maybe I16293B is a not so young star, per-haps a T-Tauri star because of its fossil outflow. However,Laurent et al. (2013) using ALMA observations proposedthat this east-west fossil outflow could also arise from thevicinities of I16293A. These ALMA observations revealeda very compact east-west bipolar outflow emanating fromthis object that maybe is the base of the large-scale out-flow.

Monitoring of IRAS 16293-2422 at centimeter wavelengthswith the VLA and now with the recently finished JVLA(Jansky Very Large Array) has allowed to detect an episodicand compact northeast-southwest ionized flow associatedwith the source IRAS 16293 A2 (Loinard et al. 2007; Pechet al. 2010), see Figure 4. This ionized flow has a a pro-jected velocity of 30-80 km s−1, and with the mass of eachejecta of the order of 10−8 M⊙. Pech et al. (2010) pro-posed that this ionized episodic outflow could energize atlarge scales the northeast-southwest molecular outflow re-ported by Wootten et al. (1989) and Mizuno et al. (1990).

Recently, 690 GHz submillimeter observations with ALMA(The Atacama Large Millimeter Array) revealed that thesource IRAS 16293 B is driving a southeast compact out-flow (Loinard et al. 2013). However, the flow has peculiarproperties: it is highly asymmetric, bubble-like, fairly slow(10 km s−1), and lacking of a jet-like feature along its sym-

8

Figure 6: ALMA Spectra in the central beams towardthe continuum peaks of IRAS 16293A (upper) and IRAS16293B (lower). In both panels is shown the detection ofthe Glycolaldehyde (HCOCH2OH) molecule. Image takenfrom Jørgensen et al. (2012).

metry axis. In addition, its dynamical age is only about200 years. In Figure 5 is shown this bubble-like outflowas revealed by the ALMA observations. However, usingthe same set of data, Kristensen et al. (2012), proposedthat this submillimeter CO emission is not associated withIRAS 16293 B, instead, a blue-shifted bow shock fromsource A is overlapping with source B in the plane of thesky. Outflow entrainment takes place over large scales, >100 AU, and wind material is decelerated through directinteraction with the envelope.

3 Molecules and Chemistry

IRAS 16293-2422 has long been considered one of the”template” sources for astrochemistry as mentioned byJørgensen et al. (2012). It has been the subject of many(sub)millimeter spectroscopic studies using single dishesand interferometers (Blake et al. 1994; van Dishoeck etal. 1995; Ceccarelli et al. 1998; Cazaux et al. 2003;Chandler et al. 2005; Caux et al. 2011; Jørgensen etal. 2011) as well as specialized modeling efforts tryingto establish its chemical composition. Particularly, thevariation in its molecular abundances as function of ra-dius has been studied (e.g., Schoier et al. 2002). Thedetections of complex molecules toward this source (e.g.,Cazaux et al. 2003; Bottinelli et al. 2004; Kuan et al.2004; Bisschop et al. 2008; Jørgensen et al. 2012) haveopened new interest in the physical processes that can leadto the evaporation of icy grain mantles. Figure 6 showsthe ALMA spectrum where the complex molecule Glyco-laldehyde (HCOCH2OH) is detected. It has also been the

target of many studies trying to relate the structure ofthe two main components to their line emission and placethem in an evolutionary scheme. As mentioned earlier thesoutheastern of the two components, IRAS 16293A, ap-pears resolved in continuum observations, breaking intoa number of different components at subarcsecond scales(Chandler et al. 2005; Pech et al. 2010). The northwest-ern component, IRAS 16293B, in contrast appears unre-solved on these scales. In terms of line emission the twosources also show significant differences: both show detec-tion of complex organic molecules (see for example: Bot-tinelli et al. 2004; Kuan et al. 2004; Remijan & Hollis2006; Bisschop et al. 2008), but the relative line strengthsand widths vary between the two sources, see Figure 6.

References:

Blake, G. A., van Dishoeck, E. F., Jansen, D. J., Groesbeck, T. D., &Mundy, L. G. 1994, ApJ, 428, 680Bisschop, S. E., Jørgensen, J. K., Bourke, T. L., Bottinelli, S., & van

Dishoeck, E. F. 2008, A&A, 488, 959Bottinelli, S.,Ceccarelli, C., Neri, R., et al. 2004, ApJL, 617, L69

Caux, E., Kahane, C., Castets, A., et al. 2011, A&A, 532, A23Cazaux, S., Tielens, A. G. G. M., Ceccarelli, C., et al. 2003, ApJL, 593,L51

Ceccarelli, C., Castets, A., Loinard, L., Caux, E., & Tielens, A. G. G. M.1998, A&A, 338, L43

Chandler, C. J., Brogan, C. L., Shirley, Y. L., & Loinard, L. 2005, ApJ,632, 371

Correia, J. C., Griffin, M., & Saraceno, P. 2004, A&A, 418, 607Estalella, R., Anglada, G., Rodriguez, L. F., & Garay, G. 1991, ApJ,371, 626

Hirano, N., Mikami, H., Umemoto, T., Yamamoto, S., & Taniguchi, Y.2001, ApJ, 547, 899

Jørgensen, J. K., Bourke, T. L., Nguyen Luong, Q., & Takakuwa, S.2011, A&A, 534, A100Jørgensen, J. K., Favre, C., Bisschop, S. E., et al. 2012, ApJL, 757, L4

Loinard, L., Torres, R. M., Mioduszewski, A. J., & Rodrıguez, L. F.2008, ApJL, 675, L29

Loinard, L., Chandler, C. J., Rodrıguez, L. F., et al. 2007, ApJ, 670,1353

Loinard, L. 2002, RMAA, 38, 61Loinard, L., Zapata, L. A., Rodrıguez, L. F., et al. 2013, MNRAS, 430,L10

Looney, L. W., Mundy, L. G., & Welch, W. J. 2000, ApJL, 529, 477Knude, J., & Hog, E. 1998, A&A, 338, 897

Kristensen, L. E., Klaassen, P. D., Mottram, J. C., Schmalzl, M., &Hogerheijde, M. R. 2013, A&A, 549, L6Kuan, Y.-J., Huang, H.-C., Charnley, S. B., et al. 2004, ApJL, 616, L27

Menten, K. M., Serabyn, E., Guesten, R., & Wilson, T. L. 1987, A&A,177, L57

Mizuno, A., Fukui, Y., Iwata, T., Nozawa, S., & Takano, T. 1990, ApJ,356, 184

Mundy, L. G., Myers, S. T., & Wilking, B. A. 1986, ApJL, 311, L75Mundy, L. G., Wootten, A., Wilking, B. A., Blake, G. A., & Sargent,A. I. 1992, ApJ, 385, 306

Pech, G., Loinard, L., Chandler, C. J., et al. 2010, ApJ, 712, 1403Pineda, J. E., Maury, A. J., Fuller, G. A., et al. 2012, A&A, 544, L7

Shu, F. H., Adams, F. C., & Lizano, S. 1987, ARAA, 25, 23Remijan, A. J., & Hollis, J. M. 2006, ApJ, 640, 842Rodrıguez, L. F., Loinard, L., D’Alessio, P., Wilner, D. J., & Ho, P. T. P.

2005, ApJL, 621, L133Walker, C. K., Lada, C. J., Young, E. T., Maloney, P. R., & Wilking,

B. A. 1986, ApJL, 309, L47Walker, C. K., Carlstrom, J. E., & Bieging, J. H. 1993, ApJ, 402, 655

Wootten, A. 1989, ApJ, 337, 858Wootten, A., & Loren, R. B. 1987, ApJ, 317, 220van Dishoeck, E. F., Blake, G. A., Jansen, D. J., & Groesbeck, T. D.

1995, ApJ, 447, 760Yeh, S. C. C., Hirano, N., Bourke, T. L., et al. 2008, ApJ, 675, 454

Schoier, F. L., Jørgensen, J. K., van Dishoeck, E. F., & Blake, G. A.2002, A&A, 390, 1001

Stark, R., Sandell, G., Beck, S. C., et al. 2004, ApJ, 608, 34Zapata, L. A., Loinard, L., Rodrıguez, L. F., et al. 2013, ApJL, 764, L14

9

Perspective

Feedback Processesby James E. Dale

The ability of infra–red and submillimetre space missionssuch as Spitzer, WISE and Herschel to see deep insidestar–forming regions has brought extraordinary advancesin our understanding of starbirth. One of the fields thathas benefitted most from this avalanche of new data isthe study of the effects of stellar feedback processes onmolecular clouds.

On scales of ∼1 up to ∼ 100 pc, the structure of thecold interstellar medium (ISM) is dominated by hot bub-bles and swept–up shells of dense, cooler material (e.g.Churchwell et al. 2006, 2007, Deharveng et al. 2010).Figure 1 shows a striking example from the WISE mission(Koenig et al., 2012). Where expanding bubbles are ableto break out of their host clouds, champagne flows result.On smaller scales on the edges of bubbles or inside them,we see pillars, cometary knots and proplyds (e.g. Smith etal. 2004, Billot et al. 2010). It is clear that the structureand appearance of most star–forming regions is governedby the action of feedback from their own stars.

What is much less clear from these observations is theeffect of feedback on the dynamical state of the cloudsand their embedded clusters, and on the star formationprocess itself on cloud scales.

A simple model of star formation in molecular clouds basedpurely on gravitational contraction and collapse results instar formation rates much higher than are observed ongalactic scales (Zuckerman & Evans, 1974). Among thesolutions proposed to this problem is the suggestion thatfeedback processes decrease the star formation efficiency

by expelling gas from clouds before it is able to collapseor be accreted (e.g. Whitworth, 1979).

Observations (e.g. Evans et al 2009) confirm that typicalstar formation efficiencies on the size–scales of molecularclouds are never more than ten percent in the Milky Way.While these efficiencies are not low enough to account forthe very slow Galactic star formation rate, they neverthe-less invite explanation.

Low star formation rates on GMC scales have a corollarythat may provide insight into another long–standing is-sue, namely the dissolution of the vast majority of stellarclusters while still very young (Lada & Lada 2003). If gasexpulsion occurs early enough and fast enough, the poten-tial well of the forming embedded cluster can in principlebecome too shallow to retain its stars (Hills 1980).

GMCs are turbulent and highly substructured, so that,even in the absence of feedback, their evolution is so com-plex that it must be modelled numerically. Increasingcomputer power and new algorithms have recently madethe inclusion of stellar feedback in such simulations possi-ble (e.g Offner et al. 2009, Krumholz et al. 2010, Walchet al 2012).

Recently Dale et al (2012a,b, 2013a,b) performed a setof smoothed–particle hydrodynamics (SPH) simulations ofthe influence of expanding HII regions on a mass–radiusparameter space of turbulent clouds. We chose the pa-rameter space to cover the observed properties of GMCsreported by Heyer et al (2009), although neglecting lowermass (∼ 103 M⊙) clouds, since they are unlikely to formany massive stars. This resulted in a set of clouds with

Figure 1: Infrared image of W3/4/5 from the WISE space-craft (Koenig et al. 2012). The width of the region shownis approximately 200pc and the bubble diameters are ap-proximately 50pc. Credit: NASA, JPL-Caltech, WISETeam.

10

Mcloud ∈ [104, 106] M⊙, Rcloud ∈ [2.5, 180] pc. Clouds wereseeded with turbulent velocity fields so that the initial ra-tios of kinetic to gravitational potential energy were either0.7 or 2.3, giving a set of bound and unbound clouds.

The clouds were allowed to evolve and form stars. They allexhibit complex structure generated by the imposed tur-bulent velocity fields. The gas forms a network of densefilaments along which gas tends to flow towards the clouds’centres of mass. This leads to the formation of stellar clus-ters at filament junctions, as has been observed by, e.g.,Schneider et al. (2012). In some cases, the filaments aredense enough to fragment along their lengths, resulting inlinear groupings of stars. However, these stars tend to fol-low the gas flow along the filaments into the nearest clusteron relatively short timescales. An example of a 105 M⊙

globally unbound cloud is shown in Figure 2.Colours rep-resent gas column densities projected along the z–axis.White dots are SPH sink particles which, in this case,represent small clusters rather than individual stars. Thefilamentary structure of the gas and the association of starformation with the filaments are clearly visible.

10−4 10−3 10−2 10−1 100

log Σ (g cm−2)

−75

−50

−25

0

25

50

75

y(p

c)

−75 −50 −25 0 25 50 75

x (pc)

Figure 2: Column density map of the 105 M⊙ globallyunbound Run UV cloud from Dale et al (2012b) beforethe onset of feedback. White dots represent star clusters.

Accretion flows inevitably result in a few stars growing tobe O–stars (in the simulations where individual stars couldbe resolved), or a few clusters growing massive enough tohost O–stars (otherwise). These objects were then given

ionizing photon fluxes appropriate to their masses and theclouds were evolved for a further 3 Myr, the approximateinterval between the formation of the first O–stars andtheir explosions as supernovae. The effects of the resultingHII regions on the clouds depends strongly on the struc-ture and properties of the clouds themselves. The massivestars and clusters are born inside the densest gas and thismaterial initially restricts the rate at which they can ionizethe gas by collimating their radiation fields. The O–starsare thus typically able to ionize only a few to ten percentof their host clouds’ total masses.

The temperature inside HII regions is fixed by an equilib-rium between heating and cooling process (Osterbrock &Ferland 2006), so that the sound speed in the ionized gashas a constant value of ≈ 10 km s−1. This is dynamicallyimportant because it sets an upper limit on the velocityto which expanding HII regions can accelerate surroundingmaterial. The ability of the HII regions to disrupt cloudsdepends on the clouds’ escape velocities. Since

vESC ∼ (Mcloud/Rcloud)1

2 ,

and the model clouds follow the observed trend of havingconstant column density, so that

Mcloud ∼ R2cloud,

it follows that

vESC ∼ (Mcloud)1

4 .

The escape velocity is then a slowly–growing function ofcloud mass. The masses of clouds in the chosen parameterspace range over two orders of magnitude, so that theescape velocity varies by a factor of a few from a few kms−1 to in excess of 10 km s−1. This relatively small rangein one particular property is the main determinant in thereaction of the clouds to their HII regions.

In lower–mass, low–vESC clouds, the HII regions destroythe filamentary gas and expand into much of the cloud vol-ume, creating ∼10pc–scale bubbles and sweeping up shellsof dense material, as shown in Figure 3. In these cases,the resulting systems bear a striking resemblance to ob-jects like W3/4/5, shown in Figure 1. In more massiveclouds, however, photoionization is unable to disrupt thefilaments and ionized gas leaks into pre–existing voids gen-erated by the imposed turbulent velocity fields. In bothcases, the permeability of the gas distribution allows largequantities of ionized gas to escape the clouds entirely. Thislowers the pressure in the HII regions and further limitsthe damage done to the clouds by feedback. These resultssuggest that other means of disrupting ∼ 106 M⊙ cloudsneed to be found.

11

10−4 10−3 10−2 10−1 100

log Σ (g cm−2)

−75

−50

−25

0

25

50

75

y(p

c)

−75 −50 −25 0 25 50 75

x (pc)

Figure 3: Column density map of the same 105 M⊙ glob-ally unbound Run UV cloud from Dale et al (2012b) after3 Myr of photoionization. White dots represent star clus-ters.

Although feedback is usually suggested as a means of lim-iting the star–forming capacity of clouds, there has alsobeen a great deal of interest in the idea that it may alsotrigger star formation (Elmegreen & Lada 1977). Thisimmediately raises the question of what is the net effectof feedback on the star–formation efficiency. This is verydifficult to answer objectively from an observational per-spective, since it requires the evaluation of a counterfac-tual argument – that of how a given system would have

evolved in the absence of feedback.

The same problem is relatively easy to approach numeri-cally, however, simply by repeating simulations with feed-back effects switched off. If this is done using a Lagrangianhydrodynamics scheme such as SPH, it allows one to de-termine not only how the star formation efficiency is al-tered by feedback, but which stars have been induced toform, prevented from forming or simply caused to formsomewhere else.

In Dale et al. (2013b), we showed that all of these pro-cesses – triggered star formation, aborted star formation,and redistribution of spontaneously–formed stars – oper-ate locally. Ionizing feedback can thus cause the geometryof star formation in a given cloud to be radically differ-ent. However, it was found that such feedback always

reduced the overall star formation efficiencies. The de-structive effects of the massive stars/clusters on the densefilaments where most star formation was taking place out-weighed any triggering taking place in outlying regions ofthe clouds.

It was also observed that the triggered objects tended to bespatially mixed with spontaneously–formed objects. Thiswas a consequence of expanding bubbles sweeping up andcompressing both gas that was going to form stars any-way, and quiescent material that would otherwise be sta-ble, and transporting it to the same locations. Thus, thegeometrical association of a given star with the edge of abubble, an ionization front, or even a pillar structure, isnot a foolproof indicator that the star has been inducedto form. This is illustrated in Figure 4 where a greyscalecolumn–density map from the Run I simulation from Daleet al. (2013b) is shown. Stars are overlaid as circles forspontaneously–formed objects and triangles for triggeredobjects, all colour–coded by mass. Note that the threeobjects near the tip of the prominent pillar in the bottomleft of the frame are not triggered.

−15 −10 −5 0 5 10 15x(pc)

−15

−10

−5

0

5

10

15

y(p

c)

−0.25

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

Log

(ste

llar

mass

) (M

⊙)Figure 4: Column density map (greyscale) of the 104 M⊙

Run I cloud from Dale et al (2013b) after 3 Myr of pho-toionization. Circles represent spontaneously–formed ob-jects and triangles denote triggered objects, all colour–coded by mass.

In reality, photoionization and winds from massive starsact simultaneously. Capriotti & Kozminski (2001) com-pared the separate influence of expanding HII regions andwinds on uniform clouds and concluded that HII regionswere likely to be more important except in very dense gas(n> 106 cm−3). McKee et al (1984), McCray & Kafatos(1987), Matzner (2002) and Fryer et al (2003, 2006) allargue that wind bubbles are likely to be trapped insideHII regions, except for the case of very massive stars or

12

very bright clusters.

These studies all rely on semi–analytic treatments or theuse of smooth initial geometries. It is not clear what thecombined effects of these two forms of feedback will beon complex turbulent clouds. It is possible that the windswould help the massive stars disrupt the dense filamentarygas in which they are born and thus reduce the collimatingeffect of this material on their radiation fields.

Once the combined outcome of ionization and winds hasbeen established, the environment in which the first su-pernovae will explode is determined. This is of crucialimportance in understanding the appearance and evolu-tion of supernova remnants. The feedback–sculpted cloudstructure will also determine what fraction of the heavyelement–polluted debris is ejected from the clouds directly,or stopped locally and immediately involved in a secondround of star formation. This latter issue has strong impli-cations for the existence of multiple generations of stars(distinguished by their metallicity) in the same clusters(e.g. Marino 2009).

References:

Billot, N.; Noriega-Crespo, A.; Carey, S.; Guieu, S.; Shenoy, S.; Pal-

adini, R.; Latter, W., 2010, ApJ 712, 797

Churchwell, E.; Povich, M. S.; Allen, D.; Taylor, M. G.; Meade,

M. R.; Babler, B. L.; Indebetouw, R.; Watson, C.; Whitney, B. A.;

Wolfire, M. G.; Bania, T. M.; Benjamin, R. A.; Clemens, D. P.;

Cohen, M.; Cyganowski, C. J.; Jackson, J. M.; Kobulnicky, H. A.;

Mathis, J. S.; Mercer, E. P.; Stolovy, S. R.; Uzpen, B.; Watson, D.

F.; Wolff, M. J., 2006, ApJ 649, 759

Capriotti, E. R.; Kozminski, J. F., 2001, PASP 113, 677

Churchwell, E.; Watson, D. F.; Povich, M. S.; Taylor, M. G.; Babler,

B. L.; Meade, M. R.; Benjamin, R. A.; Indebetouw, R.; Whitney, B.

A., 2007, ApJ 670, 428

Dale, James E.; Ercolano, Barbara; Bonnell, Ian A., 2012a, MNRAS

424, 377

Dale, James E.; Ercolano, Barbara; Bonnell, Ian A., 2012b, MNRAS

427, 2852

Dale, James E.; Ercolano, Barbara; Bonnell, Ian A., 2013a, MNRAS

430, 234

Dale, James E.; Ercolano, Barbara; Bonnell, Ian A., 2013b, MNRAS

431, 1062

Deharveng, L.; Schuller, F.; Anderson, L. D.; Zavagno, A.; Wyrowski,

F.; Menten, K. M.; Bronfman, L.; Testi, L.; Walmsley, C. M.;

Wienen, M., 2010, A&A 523, 6

Elmegreen, B. G.; Lada, C. J., 1977, ApJ 214, 725

Evans, Neal J., II; Dunham, Michael M.; Jorgensen, Jes K.; Enoch,

Melissa L.; Merin, Bruno; van Dishoeck, Ewine F.; Alcala, Juan

M.; Myers, Philip C.; Stapelfeldt, Karl R.; Huard, Tracy L.; Allen,

Lori E.; Harvey, Paul M.; van Kempen, Tim; Blake, Geoffrey A.;

Koerner, David W.; Mundy, Lee G.; Padgett, Deborah L.; Sargent,

Anneila I., 2009, ApJS 181, 321

Freyer T., Hensler G., Yorke H. W., 2003, ApJ, 594, 888

Freyer T., Hensler G., Yorke H. W., 2006, ApJ, 638, 262

Heyer, Mark; Krawczyk, Coleman; Duval, Julia; Jackson, James M.,

2009, ApJ 699, 1092

Hills, J. G., 1980, ApJ 235, 986

Koenig, X. P.; Leisawitz, D. T.; Benford, D. J.; Rebull, L. M.; Pad-

gett, D. L.; Assef, R. J., 2012, ApJ 744, 130

Krumholz, M. R.; Cunningham, A. J.; Klein, R. I.; McKee, C. F.,

2010, ApJ 713, 1120

Lada, Charles J.; Lada, Elizabeth A., 2003, ARA&A 41, 57

Marino, A. F.; Milone, A. P.; Piotto, G.; Villanova, S.; Bedin, L. R.;

Bellini, A.; Renzini, A., 2009, A&A 505, 1099

McCray R., Kafatos M., 1987, ApJ, 317, 190

McKee, C. F., van Buren D., Lazareff B., 1984, ApJL, 278, L115

Offner, S. S. R.; Klein, R. I.; McKee, C. F.; Krumholz, M. R., 2009,

ApJ 703, 131

Osterbrock, Donald E.; Ferland, Gary J., ‘Astrophysics of gaseous

nebulae and active galactic nuclei’, 2nd. ed., 2006, University Sci-

ence Books, Sausalito, CA

Schneider, N.; Csengeri, T.; Hennemann, M.; Motte, F.; Didelon,

P.; Federrath, C.; Bontemps, S.; Di Francesco, J.; Arzoumanian,

D.; Minier, V.; Andr, Ph.; Hill, T.; Zavagno, A.; Nguyen-Luong,

Q.; Attard, M.; Bernard, J.-Ph.; Elia, D.; Fallscheer, C.; Griffin,

M.; Kirk, J.; Klessen, R.; Knyves, V.; Martin, P.; Men’shchikov, A.;

Palmeirim, P.; Peretto, N.; Pestalozzi, M.; Russeil, D.; Sadavoy, S.;

Sousbie, T.; Testi, L.; Tremblin, P.; Ward-Thompson, D.; White,

G., 2012, A&A 540L, 11

Smith, Nathan; Barba, Rodolfo H.; Walborn, Nolan R., 2004, MN-

RAS 351, 1457

Walch, S.; Whitworth, A. P.; Bisbas, T.; Wunsch, R.; Hubber, D.,

2012, MNRAS 427, 625

Whitworth, A., 1979, MNRAS 186, 59

Zuckerman, B.; Evans, N. J., II. 1974, ApJ, 192, L149

13

Abstracts of recently accepted papers

A Near-Infrared Spectroscopic Study of Young Field Ultracool Dwarfs

K. N. Allers1 and Michael C. Liu2

1 Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837, USA2 Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA

E-mail contact: k.allers at bucknell.edu

We present a near-infrared (0.9–2.4 µm) spectroscopic study of 73 field ultracool dwarfs having spectroscopic and/orkinematic evidence of youth (≈10–300 Myr). Our sample is composed of 48 low-resolution (R≈100) spectra and41 moderate-resolution spectra (R≈750-2000). First, we establish a method for spectral typing M5–L7 dwarfs at near-IR wavelengths that is independent of gravity. We find that both visual and index-based classification in the near-IRprovide consistent spectral types with optical spectral types, though with a small systematic offset in the case of visualclassification at J and K band. Second, we examine features in the spectra of ∼10 Myr ultracool dwarfs to define a setof gravity-sensitive indices based on FeH, VO, K, Na, and H-band continuum shape. We then create an index-basedmethod for classifying the gravities of M6–L5 dwarfs that provides consistent results with gravity classifications fromoptical spectroscopy. Our index-based classification can distinguish between young and dusty objects. Guided by theresulting classifications, we propose a set of low-gravity spectral standards for the near-IR. Finally, we estimate theages corresponding to our gravity classifications.

Accepted by ApJ

http://arxiv.org/pdf/1305.4418

The Mass Dependence Between Protoplanetary Disks and their Stellar Hosts

Sean M. Andrews1, Katherine A. Rosenfeld1, Adam L. Kraus1 and David J. Wilner1

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

E-mail contact: sandrews at gmail.com

We present a substantial extension of the millimeter-wave continuum photometry catalog for circumstellar dust disksin the Taurus star-forming region, based on a new ”snapshot” λ = 1.3mm survey with the Submillimeter Array.Combining these new data with measurements in the literature, we construct a mm-wave luminosity distribution,f(Lmm), for Class II disks that is statistically complete for stellar hosts with spectral types earlier than M8.5 andhas a 3-σ depth of roughly 3mJy. The resulting census eliminates a longstanding selection bias against disks withlate-type hosts, and thereby demonstrates that there is a strong correlation between Lmm and the host spectral type.By translating the locations of individual stars in the Hertzsprung-Russell diagram into masses and ages, and adoptinga simple conversion between Lmm and the disk mass, Md, we confirm that this correlation corresponds to a statisticallyrobust relationship between the masses of dust disks and the stars that host them. A Bayesian regression technique isused to characterize these relationships in the presence of measurement errors, data censoring, and significant intrinsicscatter: the best-fit results indicate a typical 1.3mm flux density of ∼25mJy for 1M⊙ hosts and a power-law scalingLmm ∝ M1.5−2.0

∗ . We suggest that a reasonable treatment of dust temperature in the conversion from Lmm to Md

favors an inherently linear Md ∝ M∗ scaling, with a typical disk-to-star mass ratio of ∼0.2–0.6%. The measured RMSdispersion around this regression curve is ±0.7 dex, suggesting that the combined effects of diverse evolutionary states,dust opacities, and temperatures in these disks imprint a FWHM range of a factor of ∼40 on the inferred Md (or Lmm)at any given host mass. We argue that this relationship between Md and M∗ likely represents the origin of the inferredcorrelation between giant planet frequency and host star mass in the exoplanet population, and provides some basicsupport for the core accretion model for planet formation. Moreover, we caution that the effects of incompletenessand selection bias must be considered in comparative studies of disk evolution, and illustrate that fact with statisticalcomparisons of f(Lmm) between the Taurus catalog presented here and incomplete subsamples in the Ophiuchus, IC

14


348, and Upper Sco young clusters.

Accepted by Astrophysical Journal


Asymmetric transition disks: Vorticity or eccentricity?

S. Ataiee1,2, P. Pinilla1, A. Zsom3, C.P. Dullemond1, C. Dominik4,5 and J. Ghanbari2

1 Heidelberg University, Center for Astronomy, Institute for Theoretical Astrophysics, Albert Ueberle Str. 2, 69120Heidelberg, Germany2 Department of Physics, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran3 Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA02139, USA4 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam, theNetherlands5 Afdeling Sterrenkunde, Radboud Universiteit Nijmegen, Postbus 9010, 6500 GL, Nijmegen, the Netherlands

E-mail contact: sareh.ataiee at gmail.com

Transition disks typically appear in resolved millimeter observations as giant dust rings surrounding their young hoststars. More accurate observations with ALMA have shown several of these rings to be in fact asymmetric: theyhave lopsided shapes. It has been speculated that these rings act as dust traps, which would make them importantlaboratories for studying planet formation. It has been shown that an elongated giant vortex produced in a disk witha strong viscosity jump strikingly resembles the observed asymmetric rings. We aim to study a similar behavior fora disk in which a giant planet is embedded. However, a giant planet can induce two kinds of asymmetries: (1) agiant vortex, and (2) an eccentric disk. We studied under which conditions each of these can appear, and how one canobservationally distinguish between them. This is important because only a vortex can trap particles both radially andazimuthally, while the eccentric ring can only trap particles in radial direction. We used the FARGO code to conductthe hydro-simulations. We set up a disk with an embedded giant planet and took a radial grid spanning from 0.1 to7 times the planet semi-major axis. We ran the simulations with various viscosity values and planet masses for 1000planet orbits to allow a fully developed vortex or disk eccentricity. Afterwards, we compared the dust distributionin a vortex-holding disk with an eccentric disk using dust simulations. We find that vorticity and eccentricity aredistinguishable by looking at the azimuthal contrast of the dust density. While vortices, as particle traps, producevery pronounced azimuthal asymmetries, eccentric features are not able to accumulate millimeter dust particles inazimuthal direction, and therefore the asymmetries are expected to be modest.

Accepted by Astronomy & Astrophysics


Enhanced Hα

activity at periastron in the young and massive spectroscopic binaryHD200775

M. Benisty1,2, K. Perraut1, D. Mourard3, P. Stee3, G. Lima1, J.B. LeBouquin1, M. Borges Fernandes4,

O. Chesneau3, N. Nardetto3, I. Tallon-Bosc5, H. McAlister6,7, T. Ten Brummelaar7, S. Ridgway8, J.

Sturmann7, L. Sturmann7, N. Turner7, C. Farrington7 and P.J. Goldfinger7

1 IPAG, Grenoble, France2 MPIA, Heidelberg, Germany3 OCA, Nice, France4 Observatorio Nacional, Rio de Janeiro, Brazil5 Universite de Lyon, France6 Georgia State University, USA7 CHARA Array, USA8 NOAO, Tucson, USA

E-mail contact: Myriam.Benisty at obs.ujf-grenoble.fr

[A&A abstract abridged] Young close binaries clear central cavities in their surrounding circumbinary disk from which

15



the stars can still accrete material. This process takes place within the very first astronomical units, and is still notwell constrained as the observational evidence has been gathered, until now, only by means of spectroscopy. Duringa full orbital period (∼3.6 yrs) we observed the young massive spectroscopic binary HD200775 (separation ∼5 AU)with the VEGA instrument on the CHARA array and spatially and spectrally resolved its Hα emission, at low andmedium spectral resolutions (R∼1600 and 5000). Combining the radial velocity measurements and astrometric dataavailable in the literature, we determined new orbital parameters. We observe that the Hα equivalent width varieswith the orbital phase, and increases close to periastron, as expected from theoretical models that predict an increaseof the mass transfer from the circumbinary disk to the primary disk. In addition, we have found marginal variationsof the typical extent of the Hα emission (at 1 to 2σ level) and location (at 1 to 5σ level). The spatial extent of theHα emission, as probed by a Gaussian FWHM, is minimum at the ascending node (0.22±0.06 AU), and more thandoubles at periastron. In addition, the Gaussian photocenter is slightly displaced in the direction opposite to thesecondary, ruling out the scenario in which all or most of the emission is due to accretion onto the secondary. Thesefindings, together with the wide Hα line profile, favor a scenario in which the enhanced Hα activity at periastron maybe due to a non-spherical wind around the primary and enhanced at periastron.



Detection of 15NNH+ in L1544: non-LTE modelling of dyazenilium hyperfine line emis-sion and accurate 14N/15N values

Luca Bizzocchi1, Paola Caselli2, Elvira Leonardo1 and Luca Dore3

1 CAAUL, Observatorio Astronomico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal2 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK3 Dipartimento di Chimica ”G. Ciamician”, Universita di Bologna, via F. Selmi 2, 40126 Bologna, Italy

E-mail contact: bizzocchi at oal.ul.pt

Samples of pristine Solar System material found in meteorites and interplanetary dust particles are highly enriched in15N. Conspicuous nitrogen isotopic anomalies have also been measured in comets, and the 14N/15N abundance ratio ofthe Earth is itself larger than the recognised pre-solar value by almost a factor of two. Ion–molecules, low-temperaturechemical reactions in the proto-solar nebula have been repeatedly indicated as responsible for these 15N-enhancements.We have searched for 15N variants of the N2H

+ ion in L1544, a prototypical starless cloud core which is one of thebest candidate sources for detection owing to its low central core temperature and high CO depletion. The goal isthe evaluation of accurate and reliable 14N/15N ratio values for this species in the interstellar gas. A deep integrationof the 15NNH+ (1-0) line at 90.4GHz has been obtained with the IRAM 30m telescope. Non-LTE radiative transfermodelling has been performed on the J = 1− 0 emissions of the parent and 15N-containing dyazenilium ions, using aBonnor–Ebert sphere as a model for the source. A high-quality fit of the N2H

+ (1–0) hyperfine spectrum has allowedus to derive a revised value of the N2H

+ column density in L1544, and the analysis of the observed N15NH+ and15NNH+ spectra yielded an abundance ratio N(N15NH+)/N(15NNH+) = 1.1 ± 0.3. The obtained 14N/15N isotopicratio is ∼ 1000± 200, suggestive of a sizeable 15N depletion in this molecular ion. Such a result is not consistent withthe prediction of present nitrogen chemical models: as they predict large 15N fractionation of N2H

+, we suggest that15N14N, or 15N in some other molecular form, is preferentially depleted onto dust grains.

Accepted by Astronomy and Astrophysics


Deuterium Burning in Massive Giant Planets and Low-Mass Brown Dwarfs formed byCore-Nucleated Accretion

Peter Bodenheimer1, Gennaro D’Angelo2,4,5, Jack J. Lissauer2, Jonathan J. Fortney1, and Didier

Saumon3

1 UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA95064, USA2 Space Science and Astrobiology Division, NASA Ames Research Center, Moett Field, CA 94035, USA

16



3 Los Alamos National Laboratory, P. O. Box 1663, Los Alamos, NM 87545, USA4 SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043, USA5 Visiting Research Scientist, Los Alamos National Laboratory, Los Alamos, NM 87545, USA

E-mail contact: peter at ucolick.org

Formation of bodies near the deuterium-burning limit is considered by detailed numerical simulations according tothe core-nucleated giant planet accretion scenario. The objects, with heavy-element cores in the range 5–30 M⊕, areassumed to accrete gas up to final masses of 10–15 Jupiter masses (Mjup). After the formation process, which lasts1–5 Myr and which ends with a ’cold-start’, low-entropy configuration, the bodies evolve at constant mass up to anage of several Gyr. Deuterium burning via proton capture is included in the calculation, and we determined the mass,M50, above which more than 50% of the initial deuterium is burned. This often-quoted borderline between giantplanets and brown dwarfs is found to depend only slightly on parameters, such as core mass, stellar mass, formationlocation, solid surface density in the protoplanetary disk, disk viscosity, and dust opacity. The values for M50 fallin the range 11.6–13.6 Mjup, in agreement with previous determinations that do not take the formation process intoaccount. For a given opacity law during the formation process, objects with higher core masses form more quickly. Theresult is higher entropy in the envelope at the completion of accretion, yielding lower values of M50. For masses aboveM50, during the deuterium-burning phase, objects expand and increase in luminosity by 1 to 3 orders of magnitude.Evolutionary tracks in the luminosity-versus-time diagram are compared with the observed position of the companionto Beta Pictoris.

Accepted by ApJ


OH (1720 MHz) Masers: A Multiwavelength Study of the Interaction between theW51C Supernova Remnant and the W51B Star Forming Region

C.L. Brogan1, W.M. Goss2, T.R. Hunter1, A.M.S. Richards3, C.J. Chandler2, J.S. Lazendic4, B.-C.

Koo5, I.M. Hoffman6, and M.J. Claussen2

1 National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903, USA2 National Radio Astronomy Observatory, P. O. Box 0, Socorro, NM 87801, USA3 Jodrell Bank Centre for Astrophysics, Turing Building, University of Manchester, Manchester M13 9PL, UK4 Monash Unversity, Clayton, VIC 3800, Australia5 Astronomy Program, SEES, Seoul National University, Seoul 151-742, South Korea6 Wittenberg University, Springeld, OH 45501, USA

E-mail contact: cbrogan at nrao.edu

We present a comprehensive view of the W51B HII region complex and the W51C supernova remnant (SNR) using newradio observations from the VLA, VLBA, MERLIN, JCMT, and CSO along with archival data from Spitzer, ROSAT,ASCA, and Chandra. Our VLA data include the first 400 cm (74 MHz) continuum image of W51 at high resolution(88′′). The 400 cm image shows non-thermal emission surrounding the G49.2-0.3 HII region, and a compact source ofnon-thermal emission (W51B NT) coincident with the previously-identified OH (1720 MHz) maser spots, non-thermal21 and 90 cm emission, and a hard X-ray source. W51B NT falls within the region of high likelihood for the positionof TeV γ-ray emission. Using the VLBA three OH (1720 MHz) maser spots are detected in the vicinity of W51B NTwith sizes of 60 to 300 AU and Zeeman effect magnetic field strengths of 1.5 to 2.2 mG. The multiwavelength datademonstrate that the northern end of the W51B HII region complex has been partly enveloped by the advancingW51C SNR and this interaction explains the presence of W51B NT and the OH masers. This interaction also appearsin the thermal molecular gas which partially encircles W51B NT and exhibits narrow pre-shock (∆v ∼ 5 km s−1)and broad post-shock (∆v ∼ 20 km s−1) velocity components. RADEX radiative transfer modeling of these twocomponents yield physical conditions consistent with the passage of a non-dissociative C-type shock. Confirmation ofthe W51B/W51C interaction provides additional evidence in favor of this region being one of the best candidates forhadronic particle acceleration known thus far.

Accepted by ApJ


17



The Turbulence Power Spectrum in Optically Thick Interstellar Clouds

Blakesley Burkhart1, A. Lazarian1, V. Ossenkopf2, J. Stutzki2

1 Astronomy Department, University of Wisconsin, Madison, 475 N. Charter St., WI 53711, USA2 Physikalisches Institut der Universitat zu Koln, Zulpicher Strasse 77, 50937 Koln, Germany

E-mail contact: burkhart at astro.wisc.edu

The Fourier power spectrum is one of the most widely used statistical tools to analyze the nature of magnetohydro-dynamic turbulence in the interstellar medium. Lazarian & Pogosyan (2004) predicted that the spectral slope shouldsaturate to -3 for an optically thick medium and many observations exist in support of their prediction. However,there have not been any numerical studies to-date testing these results. We analyze the spatial power spectrum ofMHD simulations with a wide range of sonic and Alfvenic Mach numbers, which include radiative transfer effects ofthe 13CO transition. We confirm numerically the predictions of Lazarian & Pogosyan (2004) that the spectral slope ofline intensity maps of an optically thick medium saturates to -3. Furthermore, for very optically thin supersonic COgas, where the density or CO abundance values are too low to excite emission in all but the densest shock compressedgas, we find that the spectral slope is shallower than expected from the column density. Finally, we find that mixedoptically thin/thick CO gas, which has average optical depths on order of unity, shows mixed behavior: for super-Alfvenic turbulence, the integrated intensity power spectral slopes generally follow the same trend with sonic Machnumber as the true column density power spectrum slopes. However, for sub-Alfvenic turbulence the spectral slopesare steeper with values near -3 which are similar to the very optically thick regime.

Accepted by ApJ


The distance to the young open cluster Westerlund 2

Giovanni Carraro1, David Turner2, Daniel Majaess2, and Gustavo Baume3

1 ESO, Alonso de Cordova 3107, 19001, Santiago de Chile, Chile2 Department of Astronomy and Physics, Saint Marys University, Halifax, NS B3H 3C3, Canada3 Facultad de Ciencias Astronomicas y Geofısicas (UNLP), Instituto de Astrofısica de La Plata (CONICETUNLP),Paseo del Bosque s/n, La Plata, Argentina

E-mail contact: gcarraro at eso.org

A new X-ray, UBVRIc, and JHKs study of the young cluster Westerlund 2 was undertaken to resolve discrepanciestied to the cluster’s distance. Existing spectroscopic observations for bright cluster members and new multi-bandphotometry imply a reddening relation towardsWesterlund 2 described by EU−B/EB−V = 0.63+0.02 EB−V . Variable-extinction analyses for Westerlund 2 and nearby IC 2581 based upon spectroscopic distance moduli and ZAMS fittingyield values of RV = AV /EB−V = 3.88 ± 0.18 and 3.77 ± 0.19, respectively, and confirm prior assertions thatanomalous interstellar extinction is widespread throughout Carina (e.g., Turner 2012). The results were confirmedby applying the color difference method to UBVRIcJHKs data for 19 spectroscopically-observed cluster members,yielding RV = 3.85± 0.07. The derived distance to Westerlund 2 of d = 2.85± 0.43 kpc places the cluster on the farside of the Carina spiral arm. The cluster’s age is no more than τ ∼ 2× 106 yr as inferred from the cluster’s brighteststars and an X-ray (Chandra) cleaned analysis of its pre-main-sequence demographic. Four Wolf-Rayet stars in thecluster core and surrounding corona (WR20a, WR20b, WR20c, and WR20aa) are likely cluster members, and theirinferred luminosities are consistent with those of other late-WN stars in open clusters. The color-magnitude diagramfor Westerlund 2 also displays a gap at spectral type B0.5 V with associated color spread at higher and lower absolutemagnitudes that might be linked to close binary mergers. Such features, in conjunction with the evidence for mass lossfrom the WR stars, may help to explain the high flux of γ rays, cosmic rays, and X-rays from the direction towardsWesterlund 2.

Accepted by A&A


18



Observations of gas flows inside a protoplanetary gap

Simon Casassus1, Gerrit van der Plas1, Sebastian Perez M.1, William R.F. Dent2,3, Ed Fomalont4,

Janis Hagelberg5, Antonio Hales2,4, Andres Jordan6, Dimitri Mawet3, Francois Menard7,8, Al Wootten4,

David Wilner9, A. Meredith Hughes10, Matthias R. Schreiber11, Julien H. Girard3, Barbara Ercolano12,

Hector Canovas11, Pablo E. Roman13, Vachail Salinas1

1 Departamento de Astronomıa, Universidad de Chile, Casilla 36-D, Santiago, Chile2 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura 763-0355, Santiago Chile3 European Southern Observatory (ESO), Casilla 19001, Vitacura, Santiago, Chile4 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA5 Observatoire de Geneve, Universite de Geneve, 51 ch. des Maillettes, 1290, Versoix, Switzerland6 Departamento de Astronomıa y Astrofısica, Ponticia Universidad Catolica de Chile Santiago, Chile7 UMI-FCA, CNRS / INSU France (UMI 3386) , and Departamento de Astronomıa, Universidad de Chile, Santiago,Chile8 CNRS / UJF Grenoble 1, UMR 5274, Institut de Planetologie et dAstrophysique de Grenoble (IPAG), France9 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 USA10 Department of Astronomy, U. C. Berkeley, 601 Campbell Hall, Berkeley, CA 9472011 Departamento de Fısica y Astronomıa, Universidad Valparaiso, Av. Gran Bretana 111, Valparaiso, Chile12 University Observatory, Ludwig-Maximillians University, Munich13 Center of Mathematical Modeling, University of Chile, Av. Blanco Encalada 2120 Piso 7, Santiago, Chile

E-mail contact: scasassus at u.uchile.cl

Gaseous giant planet formation is thought to occur in the first few million years following stellar birth. Models predictthat giant planet formation carves a deep gap in the dust component (shallower in the gas). Infrared observationsof the disk around the young star HD142527, at ∼140 pc, found an inner disk ∼10 AU in radius, surrounded by aparticularly large gap, with a disrupted outer disk beyond 140AU, indicative of a perturbing planetary-mass body at∼90 AU. From radio observations, the bulk mass is molecular and lies in the outer disk, whose continuum emissionhas a horseshoe morphology. The vigorous stellar accretion rate would deplete the inner disk in less than a year, soin order to sustain the observed accretion, matter must flow from the outer-disk into the cavity and cross the gap.In dynamical models, the putative protoplanets channel outer-disk material into gap-crossing bridges that feed stellaraccretion through the inner disk. Here we report observations with the Atacama Large Millimetre Array (ALMA)that reveal diffuse CO gas inside the gap, with denser HCO+ gas along gap-crossing filaments, and that confirm thehorseshoe morphology of the outer disk. The estimated flow rate of the gas is in the range 7× 10−9 to 2× 10−7 M⊙

yr−1, which is sufficient to maintain accretion onto the star at the present rate.

Accepted by Nature


Alignment Between Flattened Protostellar Infall Envelopes and Ambient MagneticFields

Nicholas L. Chapman1, Jacqueline A. Davidson2, Paul F. Goldsmith3, Martin Houde4,5, Woojin Kwon6,7,

Zhi-Yun Li8, Leslie W. Looney6, Brenda Matthews9,10, Tristan G. Matthews1, Giles Novak1, Ruisheng

Peng11, John E. Vaillancourt12, Nikolaus H. Volgenau13

1 Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) & Dept. of Physics & Astronomy,Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA2 School of Physics, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia3 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 264-782, Pasadena, CA91109, USA4 Department of Physics and Astronomy, University of Western Ontario, London, ON, Canada5 Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA6 Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA7 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD, Groningen, The Netherlands8 Astronomy Department, University of Virginia, Charlottesville, VA 22904, USA9 Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC

19


V9E 2E7, Canada10 Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 1A1, Canada11 Caltech Submillimeter Observatory, 111 Nowelo Street, Hilo, HI 96720, USA12 SOFIA Science Center, Universities Space Research Association, NASA Ames Research Center, MS 232-11, MoffettField, CA 94035, USA 13 California Institute of Technology, Owens Valley Radio Observatory, Big Pine, CA 93513,USA

E-mail contact: nchapman at u.northwestern.edu

We present 350 µm polarization observations of four low-mass cores containing Class 0 protostars: L483, L1157,L1448-IRS2, and Serp-FIR1. This is the second paper in a larger survey aimed at testing magnetically regulatedmodels for core-collapse. One key prediction of these models is that the mean magnetic field in a core should bealigned with the symmetry axis (minor axis) of the flattened YSO inner envelope (aka pseudodisk). Furthermore, thefield should exhibit a pinched or hour-glass shaped morphology as gravity drags the field inward towards the centralprotostar. We combine our results for the four cores with results for three similar cores that were published in the firstpaper from our survey. An analysis of the 350 µm polarization data for the seven cores yields evidence of a positivecorrelation between mean field direction and pseudodisk symmetry axis. Our rough estimate for the probability ofobtaining by pure chance a correlation as strong as the one we found is about 5%. In addition, we combine togetherdata for multiple cores to create a source-averaged magnetic field map having improved signal-to-noise ratio, and thismap shows good agreement between mean field direction and pseudodisk axis (they are within 15◦). We also see hintsof a magnetic pinch in the source-averaged map. We conclude that core-scale magnetic fields appear to be strongenough to guide gas infall, as predicted by the magnetically regulated models. Finally, we find evidence of a positivecorrelation between core magnetic field direction and bipolar outflow axis.

Accepted by ApJ


Structure and radial equilibrium of filamentary molecular clouds

Yanett Contreras1,2, Jill Rathborne1 and Guido Garay2

1 CSIRO Astronomy and Space Science, PO Box 76, Epping NSW 1710, Australia2 Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile

E-mail contact: yanett.contreras at csiro.au

Recent dust continuum surveys have shown that filamentary structures are ubiquitous along the Galactic plane. Whilethe study of their global properties has gained momentum recently, we are still far from fully understanding their originand stability. Theories invoking magnetic field have been formulated to help explain the stability of filaments; however,observations are needed to test their predictions. In this paper, we investigate the structure and radial equilibrium offive filamentary molecular clouds with the aim of determining the role that magnetic field may play. To do this, we usecontinuum and molecular line observations to obtain their physical properties (e.g. mass, temperature and pressure).We find that the filaments have lower lineal masses compared to their lineal virial masses. Their virial parametersand shape of their dust continuum emission suggests that these filaments may be confined by a toroidal dominatedmagnetic field.

Accepted by MNRAS

http://adsabs.harvard.edu/doi/10.1093/mnras/stt720

Simulated Observations of Young Gravitationally Unstable Protoplanetary Discs

Tom Douglas1, Paola Caselli1, John Ilee2,1, Aaron Boley3, Tom Hartquist1, Richard Durisen4 and

Jonathan Rawlings5

1 chool of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK2 School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK3 Department of Astronomy, University of Florida, 211 Bryant Space Center, PO Box 112055, USA4 Department of Astronomy, Indiana University, 727 East 3rd Street, Swain West 319, Bloomington, IN 47405, USA5 Department of Physics & Astronomy, University College London, London WC1E 6BT, UK

20


http://adsabs.harvard.edu/doi/10.1093/mnras/stt720

E-mail contact: pytd at leeds.ac.uk

The formation and earliest stages of protoplanetary discs remain poorly constrained by observations. ALMA will soonrevolutionise this field. Therefore, it is important to provide predictions which will be valuable for the interpretationof future high sensitivity and high angular resolution observations. Here we present simulated ALMA observationsbased on radiative transfer modelling of a relatively massive (0.39 solar masses) self-gravitating disc embedded in a 10solar mass dense core, with structure similar to the pre-stellar core L1544. We focus on simple species and concludethat C17O 3-2, HCO+ 3-2, OCS 26-25 and H2CO 404-303 lines can be used to probe the disc structure and kinematicsat all scales.

Accepted by MNRAS


The distance to the young open cluster Westerlund 2

R. Errmann1, R. Neuhauser1, L. Marschall2, G. Torres3, M. Mugrauer1, W.P. Chen4, S.C.-L. Hu4,5,

C. Briceno6, R. Chini7,8, L. Bukowiecki9, D.P. Dimitrov10, D. Kjurkchieva11, E.L.N. Jensen12, D.H.

Cohen12, Z.-Y. Wu13, T. Pribulla14, M. Vanko14, V. Krushevska15, J. Budaj14, Y. Oasa16, A.K. Pandey17,

M. Fernandez18, A. Kellerer19, and C. Marka1

1 Astrophysikalisches Institut und Universitats-Sternwarte Jena, Schillergaßchen 2-3, D-07745 Jena, Germany2 Gettysburg College Observatory, Department of Physics, 300 North Washington St., Gettysburg, PA 17325, USA3 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Mail Stop 20, Cambridge MA 02138, USA4 Graduate Institute of Astronomy, National Central University, Jhongli City, Taoyuan County 32001, Taiwan (R.O.C.)5 Taipei Astronomical Museum, 363 Jihe Rd., Shilin, Taipei 11160, Taiwan6 Centro de Investigaciones de Astronomia, Apartado Postal 264, Merida 5101, Venezuela7 Astronomisches Institut, Ruhr-Universitat Bochum, Universitatsstr. 150, D-44801 Bochum, Germany8 Instituto de Astronomıa, Universidad Catolica del Norte, Antofagasta, Chile9 Torun Centre for Astronomy, Nicolaus Copernicus University, Gagarina 11, PL87-100 Torun, Poland10 Institute of Astronomy and NAO, Bulg. Acad. Sci., 72 Tsarigradsko Chaussee Blvd., 1784 Soa, Bulgaria11 Shumen University, 115 Universitetska str., 9700 Shumen, Bulgaria12 Dept. of Physics and Astronomy, Swarthmore College, Swarthmore, PA 19081-1390, USA13 Key Laboratory of Optical Astronomy, NAO, Chinese Academy of Sciences, 20A Datun Road, Beijing 100012,China14 Astronomical Institute, Slovak Academy of Sciences, 059 60, Tatranska Lomnica, Slovakia15 Main Astronomical Observatory of National Academy of Sciences of Ukraine, 27 Akademika Zabolotnoho St., 03680Kyiv, Ukraine16 Dept. of Astronomy and Earth Science, Saitama University, 255 Shimo-Okubo, Sakura, Saitama 338-8570, Japan17 Aryabhatta Research Institute of Observational Science, Manora Peak, Naini Tal, 263 129, Uttarakhand, India18 Instituto de Astrosica de Andalucia, CSIC, Apdo. 3004, 18080 Granada, Spain19 Department of Physics, Durham University, South Road, Durham DH1 3LE, United Kingdom

E-mail contact: ronny.errmann at uni-jena.de

With an apparent cluster diameter of 1.5◦ and an age of ∼ 4 Myr, Trumpler 37 is an ideal target for photometricmonitoring of young stars as well as for the search of planetary transits, eclipsing binaries and other sources ofvariability. The YETI consortium has monitored Trumpler 37 throughout 2010 and 2011 to obtain a comprehensiveview of variable phenomena in this region. In this first paper we present the cluster properties and membershipdetermination as derived from an extensive investigation of the literature. We also compared the coordinate list tosome YETI images. For 1872 stars we found literature data. Among them 774 have high probability of being memberand 125 a medium probability. Based on infrared data we re-calculate a cluster extinction of 0.9 – 1.2 mag. We canconfirm the age and distance to be 3 – 5 Myr and ∼ 870 pc. Stellar masses are determined from theoretical modelsand the mass function is fitted with a power-law index of α = 1.90(0.1− 0.4M⊙) and α = 1.12(1− 10M⊙).

Accepted by Astronomische Nachrichten


21



A Study of starless dark cloud LDN 1570: Distance, Dust properties and Magnetic fieldgeometry

C. Eswaraiah1, G. Maheswar1,2, A.K. Pandey1, J. Jose3, A.N. Ramaprakash4, H.C. Bhatt3

1 Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263 129, India2 Korea Astronomy and Space Science Institute, 61-1, Hwaam-dong, Yuseong-gu, Daejeon 305-348, Republic of Korea3 Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560 034, India4 Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune 411007, India

E-mail contact: eswarbramha at gmail.com

We wish to map the magnetic field geometry and to study the dust properties of the starless cloud, L1570, usingmulti-wavelength optical polarimetry and photometry of the stars projected on the cloud. We made R-band imagingpolarimetry of the stars projected on a cloud, L1570, to trace the magnetic field orientation. We also made multi-wavelength polarimetric and photometric observations to constrain the properties of dust in L1570. We estimated adistance of 394±70 pc to the cloud using 2MASS JHKs colours. Using the values of the Serkowski parameters namelyσ1, ǫ, λmax and the position of the stars on near infrared color-color diagram, we identified 13 stars that could possiblyhave intrinsic polarization and/or rotation in their polarization angles. One star, 2MASS J06075075+1934177, whichis a B4Ve spectral type, show the presence of diffuse interstellar bands in the spectrum apart from showing Hα linein emission. There is an indication for the presence of slightly bigger dust grains towards L1570 on the basis of thedust grain size-indicators such as λmax and Rv values. The magnetic field lines are found to be parallel to the cloudstructures seen in the 250 µm images (also in 8 µm and 12 µm shadow images) of L1570. Based on the magnetic fieldgeometry, the cloud structure and the complex velocity structure, we believe that L1570 is in the process of formationdue to the converging flow material mediated by the magnetic field lines. Structure function analysis showed that inthe L1570 cloud region the large scale magnetic fields are stronger when compared with the turbulent component ofmagnetic fields. The estimated magnetic field strengths suggest that the L1570 cloud region is sub-critical and hencecould be strongly supported by the magnetic field lines.

Accepted by A&A


Mass and motion of globulettes in the Rosette Nebula

G. F. Gahm1, C. M. Persson2, M. M. Makela3 and L. K. Haikala3

1 Stockholm Observatory, AlbaNova University Centre, Stockholm University, SE-106 91 Stockholm, Sweden2 Chalmers University of Technology, Department of Earth and Space Sciences, Onsala Space Observatory, SE-439 92Onsala, Sweden3 Department of Physics, PO Box 64, FI-00014 University of Helsinki, Finland

E-mail contact: gahm at astro.su.se

We have investigated tiny molecular clumps in the Rosette Nebula. In optical images these objects, so-called globulettes,appear as dark patches against the background of bright nebulosity. Radio observations were made of molecular lineemission from 16 globulettes identified in a previous optical survey. In addtion, we collected images in the NIR broad-band JHKs and narrow-band Paschen β and H2. Practically all globulettes were detected in our CO survey. Theobserved 12CO (3–2) and (2–1) line temperatures range from 0.6 K to 6 K, the 13CO being a third of this. As a rulethe lines are narrow, ∼ 1.0 kms−1.Ten objects, for which we collected information from several transitions in 12CO and 13CO were modelled using aspherically symmetric model. The best fit to observed line ratios and intensities was obtained by assuming a modelcomposed of a cool and dense centre and warm and dense surface layer. This model provides estimates of maximumand minimum mass; the average masses range from about 50 to 500 Jupiter masses, which is similar to earlierestimates based on extinction measures. The globulettes selected are dense, nH ∼ 104 cm−3, with very thin layers offluorescent H2 emission, showing that the gas is in molecular form just below the surface. The NIR data shows thatseveral globulettes are very opaque and contain dense cores. Internal gas motions are weak, but some larger objectsshow velocity-shifted components associated with tails. However, most globulettes do not show any signs of tails orpronounced bright rims. Because of the high density encountered already at the surface, the rims become thin, asevidenced by our Pβ images, which also show extended emission, that most likely comes from the backside of the

22


globulettes.We conclude that the entire complex of shells, elephant trunks, and globulettes in the northern part of the nebula isexpanding with nearly the same velocity of ∼ 22 km s−1, and with a very small spread in velocity among the globulettes.Some globulettes are in the process of detaching from elephant trunks and shells, while other more isolated objectsmust have detached long ago and are lagging behind in the general expansion of the molecular shell. We envision thatafter detachment the objects erode to isolated and dense clumps. The suggestion that some globulettes might collapseto form planetary-mass objects or brown dwarfs is strengthened by our finding of dense cores in several objects. Suchfree-floating low-mass objects would move at high speed already from the start and escape from the region.



DR 21(OH): a highly fragmented, magnetized, turbulent dense core

J. M. Girart1, P. Frau1,2, Q. Zhang3, P. M. Koch4, K. Qiu5, Y.-W. Tang4, S.-P. Lai6, P.T.P. Ho4

1 Institut de Ciencies de l’Espai, (CSIC-IEEC), Spain2 Observatorio Astronomico Nacional, Spain3 Harvard-Smithsonian Center for Astrophysics, USA4 Academia Sinica Institute of Astronomy and Astrophysics, Taiwan5 School of Astronomy and Space Science, Nanjing University, PR China6 Institute of Astronomy and Department of Physics, National Tsing Hua University, PR China

E-mail contact: girart at ice.cat

We present high-angular-resolution observations of the massive star forming core DR21(OH) at 880 µm using theSubmillimeter Array. The dense core exhibits an overall velocity gradient in a Keplerian-like pattern, which breaksat the center of the core where SMA 6 and SMA 7 are located. The dust polarization shows a complex magneticfield, compatible with a toroidal configuration. This is in contrast with the large, parsec–scale filament that surroundsthe core, where there is a smooth magnetic field. The total magnetic field strengths in the filament and in the coreare 0.9 and 2.1 mG, respectively. We found evidence of magnetic field diffusion at the core scales, far beyond theexpected value for ambipolar diffusion. It is possible that the diffusion arises from fast magnetic reconnection in thepresence of turbulence. The dynamics of the DR 21(OH) core appear to be controlled energetically in equal parts bythe magnetic field, magneto–hydrodynamic (MHD) turbulence and the angular momentum. The effect of the angularmomentum (this is a fast rotating core) is probably causing the observed toroidal field configuration. Yet, gravitationoverwhelms all the forces, making this a clear supercritical core with a mass–to–flux ratio of ≃ 6 times the criticalvalue. However, simulations show that this is not enough for the high level of fragmentation observed at 1000 AUscales. Thus, rotation and outflow feedback is probably the main cause of the observed fragmentation.

Accepted by The Astrophysical Journal


The IRAM-30m line survey of the Horsehead PDR: III. High abundance of complex(iso-)nitrile molecules in UV-illuminated gas

P. Gratier1, J. Pety1,2, V. Guzman1, M. Gerin2, J.R. Goicoechea3, E. Roue4, and A. Faure5

1 Institut de Radioastronomie Millimetrique, 300 rue de la Piscine, 38406 Saint Martin d’Heres, France2 LERMA, UMR 8112, CNRS and Observatoire de Paris, 61 avenue de l’Observatoire, 75014 Paris, France3 Centro de Astrobiologıa. CSIC-INTA. Carretera de Ajalvir, Km 4. Torrejon de Ardoz, 28850 Madrid, Spain4 LUTH UMR 8102, CNRS and Observatoire de Paris, Place J. Janssen, 92195 Meudon Cedex, France5 UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041Grenoble, France

E-mail contact: gratier at iram.fr

Complex (iso-)nitrile molecules, such as CH3CN and HC3N, are relatively easily detected in our Galaxy and in othergalaxies. We constrain their chemistry through observations of two positions in the Horsehead edge: the photo-dissociation region (PDR) and the dense, cold, and UV-shielded core just behind it. We systematically searched for

23



lines of CH3CN, HC3N, C3N, and some of their isomers in our sensitive unbiased line survey at 3, 2, and 1mm. Wederived column densities and abundances through Bayesian analysis using a large velocity gradient radiative transfermodel. We report the first clear detection of CH3NC at millimeter wavelength. We detected 17 lines of CH3CN atthe PDR and 6 at the dense core position, and we resolved its hyperfine structure for 3 lines. We detected 4 linesof HC3N, and C3N is clearly detected at the PDR position. We computed new electron collisional rate coefficientsfor CH3CN, and we found that including electron excitation reduces the derived column density by 40% at the PDRposition. While CH3CN is 30 times more abundant in the PDR than in the dense core, HC3N has similar abundanceat both positions. The isomeric ratio CH3NC/CH3CN is 0.15± 0.02. In the case of CH3CN, pure gas phase chemistrycannot reproduce the amount of CH3CN observed in the UV-illuminated gas. We propose that CH3CN gas phaseabundance is enhanced when ice mantles of grains are destroyed through photo-desorption or thermal-evaporation inPDRs, and through sputtering in shocks. (abridged)

Accepted by A&A


An Analysis of the Environments of FU Orionis Objects with Herschel

Joel D. Green1, Neal J. Evans II1, ’Agnes K’osp’al2, Gregory J. Herczeg3, Sascha P. Quanz4, Thomas

Henning5, Tim A. van Kempen6,7, Jeong-Eun Lee8, Michael M. Dunham9, Gwendolyn Meeus10, Jo-Hsin

Chen11, Manuel Guedel12, Stephen L. Skinner13, Armin Leibhart12 and Manuel Merello1

1 Department of Astronomy, 2515 Speedway, University of Texas at Austin, Austin, TX, USA2 European Space Agency (ESA/ESTEC), Keplerlaan 1, 2200 AG, Noordwijk The Netherlands3 Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, 100871, PR China4 Institute for Astronomy, ETH, Zurich, Switzerland5 Max Planck Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany6 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands7 Joint ALMA offices, Av. Alonso de Cordova 3107, Santiago, Chile8 Department of Astronomy & Space Science, Kyung Hee University, Gyeonggi 446-701, Korea9 Dept. of Astronomy, Yale University, New Haven, CT, USA10 Universidad Autonoma de Madrid, Dpt. Fisica Teorica, Campus Cantoblanco, Spain11 Jet Propulsion Laboratory, Pasadena, CA, USA12 Dept. of Astronomy, University of Vienna, Austria13 Center for Astrophysics and Space Astronomy (CASA), University of Colorado, Boulder, CO 80309-0389, USA

E-mail contact: joel at astro.as.utexas.edu

We present Herschel-HIFI, SPIRE, and PACS 50-670 µm imaging and spectroscopy of six FU Orionis-type objects andcandidates (FU Orionis, V1735 Cyg, V1515 Cyg, V1057 Cyg, V1331 Cyg, and HBC 722), ranging in outburst datefrom 1936-2010, from the FOOSH (FU Orionis Objects Surveyed with Herschel) program, as well as ancillary resultsfrom Spitzer-IRS and the Caltech Submillimeter Observatory. In their system properties (Lbol, Tbol, line emission),we find that FUors are in a variety of evolutionary states. Additionally, some FUors have features of both Class I andII sources: warm continuum consistent with Class II sources, but rotational line emission typical of Class I, far higherthan Class II sources of similar mass/luminosity. Combining several classification techniques, we find an evolutionarysequence consistent with previous mid-IR indicators. We detect [O I] in every source at luminosities consistent withClass 0/I protostars, much greater than in Class II disks. We detect transitions of 13CO (Jup of 5 to 8) around twosources (V1735 Cyg and HBC 722) but attribute them to nearby protostars. Of the remaining sources, three (FU Ori,V1515 Cyg, and V1331 Cyg) exhibit only low-lying CO, but one (V1057 Cyg) shows CO up to J = 23-22 and evidencefor H2O and OH emission, at strengths typical of protostars rather than T Tauri stars. Rotational temperatures forcool CO components range from 20-81 K, for 1050 total CO molecules. We detect [C I] and [N II] primarily as diffuseemission.

Accepted by Astrophysical Journal


24



Dynamical Evidence for a Magnetocentrifugal Wind from a 20M⊙ Binary Young StellarObject

Lincoln J. Greenhill1, Ciriaco Goddi2, Claire J. Chandler3, Lynn D. Matthews4 and Elizabeth M. L.

Humphreys5

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 USA2 Joint Institute for VLBI in Europe, Postbus 2 7990 AA, Dwingeloo, The Netherlands3 NRAO, P.O. Box O, Socorro, NM 87801, USA4 MIT Haystack Observatory, Off Route 40, Westford, MA 01886, USA5 European Southern Observatory, Karl-Schwarzschild-Strasse 2 D-85748 Garching bei Muenchen, Germany

E-mail contact: goddi at jive.nl

In Orion BN/KL, proper motions of λ7mm vibrationally-excited SiO masers trace rotation of a nearly edge-on diskand a bipolar wide-angle outflow 10-100AU from radio Source I, a binary young stellar object (YSO) of ∼20M⊙.Here we map ground-state λ7mm SiO emission with the Very Large Array and track proper motions over 9 years.The innermost and strongest emission lies in two extended arcs bracketing Source I. The proper motions trace anortheast-southwest bipolar outflow 100-1000AU from Source I with a median 3D motion of ∼18kms−1. An overlyingdistribution of λ1.3 cm H2O masers betrays similar flow characteristics. Gas dynamics and emission morphology tracedby the masers suggest the presence of a magnetocentrifugal disk-wind. Reinforcing evidence lies in the linearity of theflow, apparent rotation across the flow parallel to the disk rotation, and recollimation that narrows the flow openingangle ∼ 200AU downstream. The arcs of ground-state SiO emission may mark the transition point to a shockedsuper-Alfvenic outflow.

Accepted by ApJ Letters


MN Lup: X-rays from a weakly accreting T Tauri star

H.M. Gunther1, U. Wolter2, J. Robrade2, and S.J. Wolk1

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA2 Universitat Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany

E-mail contact: hguenther at cfa.harvard.edu

Young T Tauri stars (TTS) are surrounded by an accretion disk, which over time disperses due to photoevaporation,accretion, and possibly planet formation. The accretion shock on the central star produces an UV/optical veilingcontinuum, line emission, and X-ray signatures. As the accretion rate decreases, the impact on the central star mustchange. In this article we study MN Lup, a young star where no indications of a disk are seen in IR observations. Wepresent XMM-Newton and VLT/UVES observations, some of them taken simultaneously. The X-ray data show thatMN Lup is an active star with LX/Lbol close to the saturation limit. However, we find high densities (ne > 3 × 10cm−3) in the X-ray grating spectrum. This can be well fitted using an accretion shock model with an accretion rateof 2× 10−11 M⊙ yr−1. Despite the simple Hα line profile which has a broad component, but no absorption signaturesas typically seen on accreting TTS, we find rotational modulation in Ca ii K and in photospheric absorption lines. Inthe Hα line we see a prominence in absorption about 2R∗ above the stellar surface - the first of its kind on a TTS.MN Lup is also the only TTS where accretion is seen, but no dust disk is detected that could fuel it. We suggest thatMN Lup presents a unique and short-lived state in the disk evolution. It may have lost its dust disk only recently andis now accreting the remaining gas at a very low rate.

Accepted by ApJ


The Arches cluster out to its tidal radius: dynamical mass segregation and the effect ofthe extinction law on the stellar mass function

Maryam Habibi1,2, Andrea Stolte1, Wolfgang Brandner3, Benjamin Hußmann1, Kentaro Motohara4

1 Argelander Institut fur Astronomie, Universitat Bonn, Auf dem Hugel 71, 53121 Bonn, Germany

25



2Member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Univer-sities of Bonn and Cologne.3 Max-Planck-Institut fur Astronomie, Konigsstuhl 17, 69117 Heidelberg, Germany4 Institute of Astronomy, The University of Tokyo, Osawa 2-21-1, Mitaka, Tokyo 181-0015, Japan

E-mail contact: [email protected]

The Galactic center is the most active site of star formation in the Milky Way Galaxy, where particularly high-massstars have formed very recently and are still forming today. However, since we are looking at the Galactic centerthrough the Galactic disk, knowledge of extinction is crucial when studying this region. The Arches cluster is ayoung, massive starburst cluster near the Galactic center. We observed the Arches cluster out to its tidal radius usingKs-band imaging obtained with NAOS/CONICA at the VLT combined with Subaro/Cisco J-band data to gain a fullunderstanding of the cluster mass distribution. We show that the determination of the mass of the most massive starin the Arches cluster, which had been used in previous studies to establish an upper mass limit for the star formationprocess in the Milky Way, strongly depends on the assumed slope of the extinction law. Assuming the two regimes ofwidely used infrared extinction laws, we show that the difference can reach up to 30% for individually derived stellarmasses and ∆AKs ∼ 1 magnitude in acquired Ks-band extinction, while the present mass function slope changes by∼ 0.17 dex. The present-day mass function slope derived assuming the Nishiyama et al. (2009) extinction law increasesfrom a flat slope of αNishi = −1.50±0.35 in the core (r < 0.2 pc) to αNishi = −2.21±0.27 in the intermediate annulus(0.2 < r < 0.4 pc), where the Salpeter slope is -2.3. The present-day mass function steepens to αNishi = −3.21± 0.30in the outer annulus (0.4 < r < 1.5 pc), indicating that the outer cluster region is depleted of high-mass stars. Thispicture is consistent with mass segregation owing to the dynamical evolution of the cluster.



The Rotating Outflow, Envelope and Disk in Class-0/I protostar [BHB2007]#11 in thePipe Nebula

C. Hara1,2, Y. Shimajiri2,3, T. Tsukagoshi4, Y. Kurono2, K. Saigo2, F. Nakamura2, M. Saito2,5, D.

Wilner6 and R. Kawabe2,5

1 The University of Tokyo, 7-3-1 Hongo Bunkyo, Tokyo 113-0033, Japan2 National Astronomical Observatory of Japan, 22-21-1 Osawa Mitaka, Tokyo 181-8588, Japan3 Nobeyama Radio Observatory, 462-2 Nobeyama Minamimaki, Minamisaku District, Nagano Prefecture 384-1305,Japan4 Ibaraki University, 2-1-1 Bunkyo Mito, Ibaraki Prefecture 310-8512, Japan5 Joint ALMA Observatory, Alonso de Cordova 3107 Vitacura, Santiago 763 0355, Chile6 Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

E-mail contact: c.hara at nao.ac.jp

We present the results of observations toward a low-mass Class-0/I protostar, [BHB2007]#11 (afterwards B59#11)at the nearby (d=130 pc) star forming region, Barnard 59 (B59) in the Pipe Nebula with the Atacama SubmillimeterTelescope Experiment (ASTE) 10 m telescope (∼22′′ resolution) in CO(3–2), HCO+, H13CO+(4–3), and 1.1 mmdust-continuum emissions. We also show Submillimeter Array (SMA) data in 12CO, 13CO, C18O(2–1), and 1.3 mmdust-continuum emissions with ∼5′′ resolution. From ASTE CO(3–2) observations, we found that B59#11 is blowinga collimated outflow whose axis lies almost on the plane of the sky. The outflow traces well a cavity-like structure seenin the 1.1 mm dust-continuum emission. The results of SMA 13CO and C18O(2–1) observations have revealed thata compact and elongated structure of dense gas is associated with B59#11, which is oriented perpendicular to theoutflow axis. There is a compact dust condensation with a size of 350×180 AU seen in the SMA 1.3 mm continuummap, and the direction of its major axis is almost the same as that of the dense gas elongation. The distributions of13CO and C18O emission also show the velocity gradients along their major axes, which are considered to arise fromthe envelope/disk rotation. From the detailed analysis of the SMA data, we infer that B59#11 is surrounded by aKeplerian disk with a size of less than 350 AU. In addition, the SMA CO(2–1) image shows a velocity gradient in theoutflow along the same direction as that of the dense gas rotation. We suggest that this velocity gradient shows arotation of the outflow.

26


Accepted by ApJ


Gaps in Protoplanetary Disks as Signatures of Planets: II. Inclined Disks

H. Jang-Condell1 and N. J. Turner2,3

1 Department of Physics & Astronomy, University of Wyoming, Laramie, WY 82071, USA2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA3 Max Planck Institute for Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany

E-mail contact: neal.turner at jpl.nasa.gov

We examine the observational appearance of partial gaps being opened by planets in protoplanetary disks, consideringthe effects of the inclination relative to the line of sight. We model the disks with static α-models with detailedradiative transfer, parametrizing the shape and size of the partially cleared gaps based on the results of hydrodynamicsimulations. As in previous work, starlight falling across the gap leads to high surface brightness contrasts. Thegap’s trough is darkened by both shadowing and cooling, relative to the uninterrupted disk. The gap’s outer wall isbrightened by direct illumination and also by heating, which puffs it up so that it intercepts more starlight. In thispaper, we examine the effects of inclination on resolved images of disks with and without gaps at a wide range ofwavelengths. The scattering surface’s offset from the disk midplane creates a brightness asymmetry along the axisof inclination, making the disk’s near side appear brighter than the far side in scattered light. Finite disk thicknessalso causes the projected distances of equidistant points on the disk surface to be smaller on the near side of thedisk as compared to the far side. Consequently, the gap shoulder on the near side of the disk should appear brighterand closer to the star than on the far side. However, if the angular resolution of the observation is coarser than thewidth of the brightened gap shoulder, then the gap shoulder on the far side may appear brighter because of its largerapparent size. We present a formula to recover the scale height and inclination angle of an imaged disk using simplegeometric arguments and measuring disk asymmetries. Resolved images of circumstellar disks have revealed clearingsand gaps, such as the transitional disk in LkCa 15. Models created using our synthetic imaging attempting to matchthe morphology of observed scattered light images of LkCa 15 indicate that the H-band flux deficit in the inner ∼0.5′′

of the disk can be explained with a planet of mass greater than 0.5 Jupiter mass.

Accepted by ApJ


High-fidelity view of the structure and fragmentation of the high-mass, filamentaryIRDC G11.11-0.12

J. Kainulainen1, S.E. Ragan1, T. Henning1, and A. Stutz1

1 Max-Planck-Institute for Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany

E-mail contact: jtkainul at mpia.de

Star formation in molecular clouds is intimately linked to their internal mass distribution. We present an unprece-dentedly detailed analysis of the column density structure of a high-mass, filamentary molecular cloud, namely IRDCG11.11-0.12 (G11). We use two novel column density mapping techniques: high-resolution (FWHM=2′′, or ∼0.035pc) dust extinction mapping in near- and mid-infrared, and dust emission mapping with the Herschel satellite. Thesetwo completely independent techniques yield a strikingly good agreement, highlighting their complementarity androbustness. We first analyze the dense gas mass fraction and linear mass density of G11. We show that G11 has atop heavy mass distribution and has a linear mass density (Ml ∼ 600 M⊙ pc−1) that greatly exceeds the critical valueof a self-gravitating, non-turbulent cylinder. These properties make G11 analogous to the Orion A cloud, despite itslow star-forming activity. This suggests that the amount of dense gas in molecular clouds is more closely connectedto environmental parameters or global processes than to the star-forming efficiency of the cloud. We then examinehierarchical fragmentation in G11 over a wide range of size-scales and densities. We show that at scales 0.5 pc > l > 8pc, the fragmentation of G11 is in agreement with that of a self-gravitating cylinder. At scales smaller than l < 0.5 pc,the results agree better with spherical Jeans’ fragmentation. One possible explanation for the change in fragmentationcharacteristics is the size-scale-dependent collapse time-scale that results from the finite size of real molecular clouds:

27



at scales l < 0.5 pc, fragmentation becomes sufficiently rapid to be unaffected by global instabilities.

Accepted by A&A


The Herschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS): An overview of the 480to 1902 GHz range

M. Kama1, A. Lopez-Sepulcre2, C. Dominik1,3, C. Ceccarelli2, A. Fuente4, E. Caux5,6, R. Higgins7,

A.G.G.M. Tielens8, and T. Alonso-Albi4

1 Astronomical Institute ’Anton Pannekoek’, University of Amsterdam, Amsterdam, The Netherlands2 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno-ble, F-38041, France3 Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands4 Observatorio Astronomico Nacional, P.O. Box 112, 28803 Alcala de Henares, Madrid, Spain5 Universite de Toulouse, UPS-OMP, IRAP, Toulouse, France6 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France7 KOSMA, I. Physik. Institut, Universitat zu Koln, Zulpicher Str. 77, 50937 Koln, Germany 8 Leiden Observatory,P.O. Box 9513, NL-2300 RA, Leiden, The Netherlands

E-mail contact: M.Kama at uva.nl

Broadband spectral surveys of protostars offer a rich view of the physical, chemical and dynamical structure andevolution of star-forming regions. The Herschel Space Observatory opened up the terahertz regime to such surveys,giving access to the fundamental transitions of many hydrides and to the high-energy transitions of many other species.A comparative analysis of the chemical inventories and physical processes and properties of protostars of various massesand evolutionary states is the goal of the Herschel CHEmical Surveys of Star forming regions (CHESS) key program.This paper focusses on the intermediate-mass protostar, OMC-2 FIR 4. We obtained a spectrum of OMC-2 FIR4 in the 480 to 1902 GHz range with the HIFI spectrometer onboard Herschel and carried out the reduction, lineidentification, and a broad analysis of the line profile components, excitation, and cooling. We detect 719 spectrallines from 40 species and isotopologs. The line flux is dominated by CO, H2O, and CH3OH. The line profiles arecomplex and vary with species and upper level energy, but clearly contain signatures from quiescent gas, a broadcomponent likely due to an outflow, and a foreground cloud. We find abundant evidence for warm, dense gas, as wellas for an outflow in the field of view. Line flux represents 2% of the 7 L⊙ luminosity detected with HIFI in the 480to 1250 GHz range. Of the total line flux, 60% is from CO, 13% from H2O and 9% from CH3OH. A comparison withsimilar HIFI spectra of other sources is set to provide much new insight into star formation regions, a case in pointbeing a difference of two orders of magnitude in the relative contribution of sulphur oxides to the line cooling of OrionKL and OMC-2 FIR 4.

Accepted by A&A


ALMA detection of the rotating molecular disk wind from the young star HD 163296

P.D. Klaassen1, A. Juhasz1, G.S. Mathews1, J.C. Mottram1, I. De Gregorio-Monsalvo2,3, E.F. van

Dishoeck1,4, S. Takahashi5, E. Akiyama6, A. Hales2, M.R. Hogerheijde1, M. Rawlings7, M. Schmalzl1

and L. Testi3,8

1 Leiden Observatory , Leiden University, P.O. Box 9513, 2300 RA, Leiden, The Netherlands2 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile3 European Southern Observatory, Karl Schwarzschild Str 2, 85748, Garching, Germany4 Max-Planck-Institut fur Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany5 Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan6 National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan7 NRAO, 520 Edgemont Road, Charlottesville, VA 22903, USA8 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125, Firenze, Italy

28



E-mail contact: klaassen at strw.leidenuniv.nl

Disk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades.HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a series of HH knots (HH 409)with bow shocks associated with the farthest knots. Here we present ALMA Science Verification data of CO J=2-1and J=3-2 emission which are spatially coincident with the blue shifted jet of HH knots, and offset from the diskby -18.6 km s−1. The emission has a double corkscrew morphology and extends more than 10′′ from the disk withembedded emission clumps coincident with jet knots. We interpret this double corkscrew as emission from material ina molecular disk wind, and that the compact emission near the jet knots is being heated by the jet which is moving atmuch higher velocities. We show that the J=3-2 emission is likely heavily filtered by the interferometer, but the J=2-1emission suffers less due to the larger beam and measurable angular scales. Excitation analysis suggests temperaturesexceeding 900 K in these compact features, with the wind mass, momentum and energy being of order 10−5 M⊙, 10

−4

M⊙ km s−1 and 1040 erg respectively. The high mass loss rate suggests that this star is dispersing the disk faster thanit is funneling mass onto the star.



On the simultaneous evolution of massive protostars and their host cores

Rolf Kuiper1 and Harold W. Yorke1

1 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

E-mail contact: Rolf.Kuiper at jpl.nasa.gov

Studies of the evolution of massive protostars and the evolution of their host molecular cloud cores are commonlytreated as separate problems. However, interdependencies between the two can be significant. Here, we study thesimultaneous evolution of massive protostars and their host molecular cores using a multi-dimensional radiation hydro-dynamics code that incorporates the effects of the thermal pressure and radiative acceleration feedback of the centrallyforming protostar. The evolution of the massive protostar is computed simultaneously using the stellar evolution codeSTELLAR, modified to include the effects of variable accretion. The interdependencies are studied in three differentcollapse scenarios. For comparison, stellar evolutionary tracks at constant accretion rates and the evolution of thehost cores using pre-computed stellar evolutionary tracks are computed. The resulting interdependencies of the pro-tostellar evolution and the evolution of the environment are extremely diverse and depend on the order of events, inparticular the time of circumstellar accretion disk formation with respect to the onset of the bloating phase of the star.Feedback mechanisms affect the instantaneous accretion rate and the protostar’s radius, temperature and luminosityon timescales equal or smaller than 5 kyr, corresponding to the accretion timescale and Kelvin-Helmholtz contractiontimescale, respectively. Nevertheless, it is possible to approximate the overall protostellar evolution in many cases bypre-computed stellar evolutionary tracks assuming appropriate constant average accretion rates.

Accepted by ApJ


The reliability of approximate radiation transport methods for irradiated disk studies

Rolf Kuiper1,2 and Ralf S. Klessen3

1 Universitaet Tuebingen, Institut fuer Astronomie und Astrophysik, Computational Physics, Auf der Morgenstelle10, D-72076 Tuebingen, Germany2 Max-Planck-Institut fuer Astronomie Heidelberg, Koenigstuhl 17, D-69117 Heidelberg, Germany3 Universitaet Heidelberg, Zentrum fuer Astronomie Heidelberg, Institut fuer theoretische Astrophysik, Albert-Ueberle-Strasse 2, D-69120 Heidelberg, Germany

E-mail contact: rolf.kuiper at uni-tuebingen.de

Context: Dynamical studies of irradiated circumstellar disks require an accurate treatment of radiation transport to,for example, properly determine cooling and fragmentation properties. At the same time the radiation transportalgorithm should be as fast as the (magneto-) hydrodynamics to allow for an efficient usage of computing resources.

29



Such fast radiation transport methods imply the acceptance of far-reaching approximations.Aims: We check the reliability of fast, approximate radiation transport methods for circumstellar disk studies bycomparing their accuracy to previous standard radiation benchmark test results.Methods: We use different approximate radiation transport methods and compute the equilibrium temperature dis-tribution in a setup of a central star and a slightly flared circumstellar disk, which is embedded in an optically thinenvelope. We perform simulations for a wide range of optical depths of the disk’s midplane from τ550nm = 0.1 up toτ810nm = 1.22 × 106 . We check the accuracy of the gray flux-limited diffusion (FLD) approximation and the grayand frequency-dependent hybrid approximation. In the hybrid method, the stellar irradiation is computed via a grayor frequency-dependent ray-tracing (RT) step and the thermal (re-)emission by dust grains is shifted to a gray FLDsolver.Results: 1. For moderate optical depths, a gray approximation of the stellar irradiation yields a slightly hotter innerrim and a slightly cooler midplane of the disk at larger radii, but is otherwise in agreement with the frequency-dependent treatment.2. The gray FLD approximation fails to compute an appropriate temperature profile in all regimes of optical depth;the maximum deviations to the comparison runs are 50% in the optically thin and up to 280% in the optically thicklimit. For low optical depth, the isotropic assumption within the FLD method yields a too steep decrease of the radialtemperature slope. For higher optical depths, the FLD approximation does not reproduce the shadow behind theoptically thick inner rim of the circumstellar disk, yielding artificial heating at larger disk radii.3. The frequency-dependent RT + gray FLD approximation yields remarkable accuracy for the whole range of opticaldepths.Conclusions: The high accuracy of the frequency-dependent hybrid radiation transport algorithm makes this methodideally suited for (magneto-) hydrodynamical studies of irradiated circumstellar disks.



Spectral variability of classical T Tauri stars accreting in an unstable regime

Ryuichi Kurosawa1,2 and Marina M. Romanova1

1 Department of Astronomy, Cornell University, Ithaca, NY 14853-6801, USA2 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany

E-mail contact: kurosawa at mpifr-bonn.mpg.de

Classical T Tauri stars (CTTSs) are variable in different time-scales. One type of variability is possibly connectedwith the accretion of matter through the Rayleigh-Taylor instability that occurs at the interface between an accretiondisc and a stellar magnetosphere. In this regime, matter accretes in several temporarily formed accretion streamsor ‘tongues’ which appear in random locations, and produce stochastic photometric and line variability. We use theresults of global three-dimensional magnetohydrodynamic simulations of matter flows in both stable and unstableaccretion regimes to calculate time-dependent hydrogen line profiles and study their variability behaviours. In thestable regime, some hydrogen lines (e.g. Hβ, Hγ, Hδ, Paβ and Brγ) show a redshifted absorption component onlyduring a fraction of a stellar rotation period, and its occurrence is periodic. However, in the unstable regime, theredshifted absorption component is present rather persistently during a whole stellar rotation cycle, and its strengthvaries non-periodically. In the stable regime, an ordered accretion funnel stream passes across the line of sight toan observer only once per stellar rotation period while in the unstable regime, several accreting streams/tongues,which are formed randomly, pass across the line of sight to an observer. The latter results in the quasi-stationarityappearance of the redshifted absorption despite the strongly unstable nature of the accretion. In the unstable regime,multiple hot spots form on the surface of the star, producing the stochastic light curve with several peaks per rotationperiod. This study suggests a CTTS that exhibits a stochastic light curve and a stochastic line variability, with arather persistent redshifted absorption component, may be accreting in the unstable accretion regime.

Accepted by MNRAS


30



Protostellar Disk Evolution Over Million-Year Timescales with a Prescription for Mag-netized Turbulence

Russell Landry1, Sarah E. Dodson-Robinson2, Neal J. Turner3, and Greg Abram4

1 Physics Department, University of Texas at Dallas2 Astronomy Department, University of Texas at Austin3 Jet Propulsion Laboratory/California Institute of Technology4 Texas Advanced Computing Center, University of Texas at Austin

E-mail contact: russell.landry at gmail.com

Magnetorotational instability (MRI) is the most promising mechanism behind accretion in low-mass protostellar disks.Here we present the first analysis of the global structure and evolution of non-ideal MRI-driven T-Tauri disks on million-year timescales. We accomplish this in a 1+1D simulation by calculating magnetic diffusivities and utilizing turbulenceactivity criteria to determine thermal structure and accretion rate without resorting to a 3-D magnetohydrodynamical(MHD) simulation. Our major findings are as follows. First, even for modest surface densities of just a few times theminimum-mass solar nebula, the dead zone encompasses the giant planet-forming region, preserving any compositionalgradients. Second, the surface density of the active layer is nearly constant in time at roughly 10 g cm−2, which weuse to derive a simple prescription for viscous heating in MRI-active disks for those who wish to avoid detailed MHDcomputations. Furthermore, unlike a standard disk with constant-α viscosity, the disk midplane does not cool off overtime, though the surface cools as the star evolves along the Hayashi track. The ice line is firmly in the terrestrialplanet-forming region throughout disk evolution and can move either inward or outward with time, depending onwhether pileups form near the star. Finally, steady-state mass transport is a poor description of flow through anMRI-active disk. We caution that MRI activity is sensitive to many parameters, including stellar X-ray flux, grainsize, gas/small grain mass ratio and magnetic field strength, and we have not performed an exhaustive parameterstudy here.

Accepted by ApJ


Distribution of HNCO 505 − 404 in Massive Star-forming Regions

Juan Li1,2,3, Junzhi Wang1,2, Qiusheng Gu1,2, and Xingwu Zheng1,2

1 School of Astronomy & Space Science, Nanjing University, 22 Hankou RD, Nanjing 210093, China2 Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing210093, China3 Shanghai Astronomical Observatory, CAS, 80 Nandan Road, Shanghai 200030, China

E-mail contact: lijuan at shao.ac.cn

The goal of this paper is to study the spatial distribution of HNCO in massive star-forming regions, and investigateits spatial association with infrared sources, as well as physical conditions in region of HNCO emission. We havemapped nine massive star-forming regions in HNCO 505−404 with the Purple Mountain Observatory 13.7m telescope.The C18O maps of these sources were obtained simultaneously. The HNCO emission shows compact distribution,with emission peak centred on water masers. Nearly all the HNCO clumps show signs of embedded mid-infrared orfar-infrared sources. The FWHM sizes of HNCO clumps are significantly smaller than C18O clumps but rather similarto HC3N clumps. We also found good correlation between the integrated intensities, linewidths and LSR velocities ofHNCO and HC3N emission, implying similar excitation mechanism of these two species. As such, collisional excitationis likely to be the dominant excitation mechanism for HNCO 505−404 emission in galactic massive star-forming regions.

Accepted by A&A


High angular resolution observations towards OMC-2 FIR 4: Dissecting an intermediate-mass protocluster

A. Lopez-Sepulcre1, V. Taquet1, A. Sanchez-Monge2, C. Ceccarelli1, C. Dominik3,4, M. Kama3, E.

31



Caux5,6, F. Fontani2, A. Fuente7, P.T.P. Ho8,9, R. Neri10 and Y. Shimajiri11

1 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno-ble, F-38041, France2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50124 Firenze, Italy3 Astronomical Institute Anton Pannekoek, University of Amsterdam, Amsterdam, The Netherlands4 Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands5 Universite de Toulouse, UPS-OMP, IRAP, Toulouse, France6 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France7 Observatorio Astronomico Nacional, P.O. Box 112, 28803 Alcala de Henares, Madrid, Spain8 Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan9 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA10 IRAM, 300 rue de la piscine, F-38406 Saint-Martin d’Heres, France11 Nobeyama Radio Observatory, 462-2 Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan

E-mail contact: ana.sepulcre at obs.ujf-grenoble.fr

Context. Intermediate-mass stars are an important ingredient of our Galaxy and a key to understanding how high-and low-mass stars form in clusters. One of the closest known young intermediate-mass protoclusters is OMC-2 FIR 4,which is located at a distance of 420 pc in Orion. This region is one of the few where the complete 500-2000 GHzspectrum has been observed with the heterodyne spectrometer HIFI on board the Herschel satellite, and unbiasedspectral surveys at 0.8, 1, 2, and 3 mm have been obtained with the JCMT and IRAM 30-m telescopes.Aims. We aim to disentangle the core multiplicity, to investigate the morphology of this region in order to study theformation of a low- and intermediate-mass protostar cluster, and to aid in interpretation of the single-dish line profilesalready in our hands.Methods. We used the IRAM Plateau de Bure Interferometer to image OMC-2 FIR 4 in the 2-mm continuum emission,as well as in DCO+(2–1), DCN(2–1), C34S(3–2), and several CH3OH lines. In addition, we analysed observations ofthe NH3(1,1) and (2,2) inversion transitions that used the Very Large Array of the NRAO. The resulting maps havean angular resolution that allows us to resolve structures of 5′′, which is equivalent to 2000 AU.Results. Our observations reveal three spatially resolved sources within OMC-2 FIR 4, of one or several solar masseseach, with hints of further unresolved substructure within them. Two of these sources have elongated shapes and areassociated with dust continuum emission peaks, thus likely containing at least one molecular core each. One of themalso displays radio continuum emission, which may be attributed to a young B3-B4 star that dominates the overallluminosity output of the region. The third identified source displays a DCO+(2–1) emission peak and weak dustcontinuum emission. Its higher abundance of DCO+ relative to the other two regions suggests a lower temperature,hence its possible association with either a younger low-mass protostar or a starless core. It may alternatively be partof the colder envelope of OMC-2 FIR 4.Conclusions. Our interferometric observations show the complexity of the intermediate-mass protocluster OMC-2 FIR 4, where multiple cores, chemical dierentiation, and an ionised region all coexist within an area of only 10000 AU.



Misaligned streamers around a galactic centre black hole from a single cloud’s infall

W.E. Lucas1, I.A. Bonnell1, M.B. Davies2 and W.K.M. Rice3

1 SUPA, School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK2 Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-221 00 Lund, Sweden3 SUPA, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK

E-mail contact: wel2 at st-andrews.ac.uk

We follow the near radial infall of a prolate cloud onto a 4 × 106M⊙ supermassive black hole in the Galactic Centreusing smoothed particle hydrodynamics (SPH). We show that a prolate cloud oriented perpendicular to its orbitalplane naturally produces a spread in angular momenta in the gas which can translate into misaligned discs as is seenin the young stars orbiting Sagittarius A*. A turbulent or otherwise highly structured cloud is necessary to avoidcancelling too much angular momentum through shocks at closest approach. Our standard model of a 2 × 104M⊙

32


gas cloud brought about the formation of a disc within 0.3 pc from the black hole and a larger, misaligned streamerat 0.5 pc. A total of 1.5 × 104M⊙ of gas formed these structures. Our exploration of the simulation parameter spaceshowed that when star formation occurred, it resulted in top-heavy IMFs with stars on eccentric orbits with semi-major axes 0.02 to 0.3 pc and inclinations following the gas discs and streamers. We suggest that the single event ofan infalling prolate cloud can explain the occurrence of multiple misaligned discs of young stars.

Accepted by MNRAS


Identifying gaps in flaring Herbig Ae/Be disks using spatially resolved mid-infraredimaging. Are all group I disks transitional?

K.M. Maaskant1,2, M. Honda3, L.B.F.M. Waters4,2, A.G.G.M. Tielens1, C. Dominik2,5, M. Min2, A.

Verhoeff2, G. Meeus6, and M.E. van den Ancker7

1 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands2 Anton Pannekoek Astronomical Institute, University of Amsterdam, P.O. Box 94249, 1090 GE Amsterdam, TheNetherlands3 Department of Mathematics and Physics, Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kana-gawa, 259-1293, Japan4 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands5 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010 6500 GL Nijmegen, The Nether-lands6 Universidad Autonoma de Madrid, Dpt. Fisica Teorica, Campus Cantoblanco, Spain7 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching b. Munchen, Germany

E-mail contact: maaskant at strw.leidenuniv.nl

Context. The evolution of young massive protoplanetary disks toward planetary systems is expected to include theformation of gaps and the depletion of dust and gas.Aims. A special group of flaring disks around Herbig Ae/Be stars do not show prominent silicate emission features.We focus our attention on four key Herbig Ae/Be stars to understand the structural properties responsible for theabsence of silicate feature emission.Methods. We investigate Q- and N-band images taken with Subaru/COMICS, Gemini South/T-ReCS and VLT/VISIR.Our radiative transfer modeling solutions require a separation of inner- and outer- disks by a large gap. From this wecharacterize the radial density structure of dust and PAHs in the disk.Results. The inner edge of the outer disk has a high surface brightness and a typical temperature between ∼100–150K and therefore dominates the emission in the Q-band. We derive radii of the inner edge of the outer disk of 34,23, 30 and 63 AU for HD97048, HD169142, HD135344B and Oph IRS 48 respectively. For HD97048 this is the firstdetection of a disk gap. The continuum emission in the N-band is not due to emission in the wings of PAHs. Thiscontinuum emission can be due to VSGs or to thermal emission from the inner disk. We find that PAH emission isnot always dominated by PAHs on the surface of the outer disk.Conclusions. The absence of silicate emission features is due to the presence of large gaps in the critical temperatureregime. Many, if not all Herbig disks with Spectral Energy Distribution (SED) classification ’group I’ are disks withlarge gaps and can be characterized as (pre-) transitional. An evolutionary path from the observed group I to theobserved group II sources seems no longer likely. Instead, both might derive from a common ancestor.

Accepted by A&A


Physical characteristics of G331.5-0.1: The luminous central region of a Giant MolecularCloud

Manuel Merello1,3, Leonardo Bronfman1, Guido Garay1, Lars-Ake Nyman2, Neal J. Evans II3 and C.

Malcolm Walmsley4,5

1 Departamento de Astronomıa, Universidad de Chile, Casilla 36-D, Santiago, Chile

33



2 Joint ALMA Observatory (JAO), Alonso de Cordova 3107, Vitacura, Santiago, Chile3 University of Texas at Austin, 1 University Station, Austin, Texas, 78712, USA4 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy5 Dublin Institute of Advanced Studies, Fitzwilliam Place 31, Dublin 2, Ireland

E-mail contact: manuel at astro.as.utexas.edu

We report molecular line and dust continuum observations toward the high-mass star forming region G331.5-0.1, oneof the most luminous regions of massive star-formation in the Milky Way, located at the tangent region of the Normaspiral arm, at a distance of 7.5 kpc. Molecular emission was mapped toward the G331.5-0.1 GMC in the CO(J = 1 →0)and C18O(J = 1 →0) lines with NANTEN, while its central region was mapped in CS(J = 2 → 1 and J = 5 → 4)with SEST, and in CS(J = 7 →6) and 13CO(J = 3 →2) with ASTE. Continuum emission mapped at 1.2 mm withSIMBA and at 0.87 mm with LABOCA reveal the presence of six compact and luminous dust clumps, making thissource one of the most densely populated central regions of a GMC in the Galaxy. The dust clumps are associatedwith molecular gas and they have the following average properties: size of 1.6 pc, mass of 3.2 × 103 M⊙, molecularhydrogen density of 3.7× 104 cm−3, dust temperature of 32 K, and integrated luminosity of 5.7× 105 L⊙, consistentwith values found toward other massive star forming dust clumps. The CS and 13CO spectra show the presence of twovelocity components: a high-velocity component at ∼ −89 km s−1, seen toward four of the clumps, and a low-velocitycomponent at ∼ −101 km s−1 seen toward the other two clumps. Radio continuum emission is present toward four ofthe molecular clumps, with spectral index estimated for two of them of 0.8±0.2 and 1.2±0.2. A high-velocity molecularoutflow is found at the center of the brightest clump, with a line width of 26 km s−1 (FWHM) in CS(J = 7 →6) .Observations of SiO(J = 7 → 6 and J = 8 → 7), and SO(JK = 88 → 77 and JK = 87 → 76) lines provide estimates ofthe gas rotational temperature toward this outflow >120 K and > 75 K, respectively.



Resolved Giant Molecular Clouds in Nearby Spiral Galaxies: Insights from the CANONCO (1-0) Survey

Jennifer Donovan Meyer1,2, Jin Koda1, Rieko Momose3,4,5, Thomas Mooney1, Fumi Egusa6,7, MistyCarty8,

Robert Kennicutt9, Nario Kuno10,11, David Rebolledo12, Tsuyoshi Sawada4,13, Nick Scoville7, Tony

Wong12

1 Department of Physics & Astronomy, Stony Brook University, Stony Brook, NY 117942 National Radio Astronomy Observatory, Charlottesville, VA 229013 Department of Astronomy, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan4 National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan5 Institute for Cosmic Ray Research, University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba, 277-8582, Japan6 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Chuo-ku, Sagamihara, Kanagawa252-5210, Japan7 Department of Astronomy, California Institute of Technology, Pasadena, CA 911258 Department of Astronomy, University of Maryland, College Park, MD 207429 Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, United Kingdom10 Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano, 384-1305, Japan11 The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-001512 Astronomy Department, University of Illinois, Urbana, IL 6180113 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago 763-0355, Chile

E-mail contact: jdonovanmeyer at gmail.com

We resolve 182 individual giant molecular clouds (GMCs) larger than 2.5 × 105 M⊙ in the inner disks of five largenearby spiral galaxies (NGC 2403, NGC 3031, NGC 4736, NGC 4826, and NGC 6946) to create the largest suchsample of extragalactic GMCs within galaxies analogous to the Milky Way. Using a conservatively chosen sample ofGMCs most likely to adhere to the virial assumption, we measure cloud sizes, velocity dispersions, and 12CO (J=1-0)luminosities and calculate cloud virial masses. The average conversion factor from CO flux to H2 mass (or XCO) foreach galaxy is (1 − 2)× 1020 cm−2 / (K km s−1), all within a factor of two of the Milky Way disk value (∼ 2 × 1020

cm−2 / (K km s−1). We find GMCs to be generally consistent within our errors between the galaxies and with Milky

34


Way disk GMCs; the intrinsic scatter between clouds is of order a factor of two. Consistent with previous studies in theLocal Group, we find a linear relationship between cloud virial mass and CO luminosity, supporting the assumptionthat the clouds in this GMC sample are gravitationally bound. We do not detect a significant population of GMCswith elevated velocity dispersions for their sizes, as has been detected in the Galactic center. Though the range ofmetallicities probed in this study is narrow, the average conversion factors of these galaxies will serve to anchor thehigh metallicity end of metallicity-XCO trends measured using conversion factors in resolved clouds; this has beenpreviously possible primarily with Milky Way measurements.

Accepted by ApJ


Dynamics, CO depletion, and deuterium fractionation of the dense condensations withinthe fragmented prestellar core Orion B9–SMM 6

Oskari Miettinen1 and Stella S. R. Offner2

1 Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland2 Department of Astronomy, Yale University, New Haven, CT 06511, USA

E-mail contact: oskari.miettinen at helsinki.fi

Context. Low-mass prestellar cores are rarely found to be fragmented into smaller condensations but studying suchsubstructure where present is essential for understanding the origin of multiple stellar systems.Aims. We attempt to better understand the kinematics and dynamics of the subfragments inside the prestellar coreSMM 6 in Orion B9. Another object of the present study is to constrain the evolutionary stage of the condensationsby investigating the levels of CO depletion and deuterium fractionation.Methods. We used the APEX telescope to observe the molecular lines C17O(2 − 1), N2H

+(3 − 2), and N2D+(3 − 2)

towards the condensations. We use the line data in conjunction with our previous SABOCA 350-µm dust continuummap of the source.Results. The condensations are characterised by subsonic internal non-thermal motions (σNT ≃ 0.5cs), and most ofthem appear to be gravitationally bound. The dispersion of the N2H

+ velocity centroids among the condensations isvery low (0.02 km s−1). The CO depletion factors we derive, fD = 0.8± 0.4− 3.6± 1.5, do not suggest any significantCO freeze-out but this may be due to the canonical CO abundance we adopt. The fractional abundances of N2H

+

and N2D+ with respect to H2 are found to be ∼ 0.9− 2.3× 10−9 and ∼ 4.9− 9.9× 10−10, respectively. The deuterium

fractionation of N2H+ lies in the range 0.30± 0.07− 0.43± 0.09.

Conclusions. The detected substructure inside SMM 6 is likely the result of cylindrical Jeans-type gravitationalfragmentation. We estimate the timescale for this fragmentation to be ∼ 1.8× 105 yr. The condensations are unlikelyto be able to interact with one another and coalesce before local gravitational collapse ensues. Moreover, significantmass growth of the condensations via competitive-like accretion from the parent core seems unfeasible. The high levelof molecular deuteration in the condensations suggests that gas-phase CO should be strongly depleted. It also pointstowards an advanced stage of chemical evolution. The subfragments of SMM 6 might therefore be near the onset ofgravitational collapse, but whether they can form protostellar or substellar objects (brown dwarfs) depends on thelocal star formation efficiency and remains to be clarified.



Precise radial velocities of giant stars V. A brown dwarf and a planet orbiting the Kgiant stars tau Gem and 91 Aqr

David S. Mitchell1,2, Sabine Reffert1, Trifon Trifonov1, Andreas Quirrenbach1 and Debra A. Fischer3

1 Landessternwarte, Zentrum fr Astronomie der Universitt Heidelberg, Knigstuhl 12, 69117 Heidelberg, Germany2 Physics Department, California Polytechnic State University, San Luis Obispo, CA, 93407, USA3 Department of Astronomy, Yale University, New Haven, CT, 06511, USA

E-mail contact: dsmitche at calpoly.edu

We aim to detect and characterize substellar companions to K giant stars to further our knowledge of planet formation

35



and stellar evolution of intermediate-mass stars. For more than a decade we have used Doppler spectroscopy to acquirehigh-precision radial velocity measurements of K giant stars. All data for this survey were taken at Lick Observatory.Our survey includes 373 G and K giants. Radial velocity data showing periodic variations were fitted with Keplerianorbits using a χ2 minimization technique. We report the presence of two substellar companions to the K giant starsτ Gem and 91 Aqr. The brown dwarf orbiting τ Gem has an orbital period of 305.5± 0.1 days, a minimum mass of20.6 MJ, and an eccentricity of 0.031± 0.009. The planet orbiting 91 Aqr has an orbital period of 181.4± 0.1 days,a minimum mass of 3.2 MJ, and an eccentricity of 0.027± 0.026. Both companions have exceptionally circular orbitsfor their orbital distance, as compared to all previously discovered planetary companions.

Accepted by A&A


Protoplanetary Disk Masses from Stars to Brown Dwarfs

Subhanjoy Mohanty1, Jane Greaves2, Daniel Mortlock1, Ilaria Pascucci3, Aleks Scholz4, Mark Thompson5,

Daniel Apai3,6, Giuseppe Lodato7, Dagny Looper8

1 Imperial College London, 1010 Blackett Lab, Prince Consort Rd, London SW7 2AZ, UK2 SUPA, Physics & Astronomy, Univ. of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK3 Dept. of Planetary Sciences and Lunar and Planetary Lab, Univ. of Arizona, Tucson AZ 85721, USA4 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland5 Ctr. for Astrophysics Research, Univ. of Hertfordshire, College Lane, Hatfield AL10 9AB, UK6 Dept. of Astronomy and Steward Observatory, Univ. of Arizona, Tucson, AZ 85721, USA7 Dipartimento di Fisica, Universita Degli Studi di Milano, Via Celoria, 16 Milano, 20133, Italy8 Institute for Astronomy, Univ. of Hawai’i, 2680 Woodlawn Dr, Honolulu, HI 96822, USA.

E-mail contact: s.mohanty at imperial.ac.uk

We present SCUBA-2 850µm observations for 7 very low mass stars (VLMS) and brown dwarfs (BDs): 3 in Taurus, 4in the TWA, and all classical T Tauri (cTT) analogs. We detect 2 of the 3 Taurus disks, but none of the TWA ones.Our 3σ limits correspond to a dust mass of 1.2 M⊕ in Taurus and a mere 0.2 M⊕ in the TWA (3–10× deeper thanprevious work). We combine our data with other sub-mm/mm surveys of Taurus, ρ Oph and the TWA to investigatetrends in disk mass and grain growth during the cTT phase. We find : (1) The minimum disk outer radius required toexplain the upper envelope of sub-mm/mm fluxes is 100 AU for intermediate-mass stars, solar-types and VLMS, and20 AU for BDs. (2) While the upper envelope of disk masses increases with M∗ from BDs to VLMS to solar-types,no increase is seen from solar-type to intermediate-mass stars. We propose this is due to enhanced photoevaporationaround intermediate masses. (3) Many disks around Taurus and ρ Oph intermediate-mass and solar-type stars evincean opacity index β of 0–1, indicating large grains. Of the only four VLMS/BDs in these regions with multi-wavelengthdata, three are consistent with large grains, though optically thick disks are not ruled out. (4) For the TWA VLMS(TWA 30A, B), combining our fluxes with M and ages suggests substantial grain growth by 10 Myr. The degree ofgrain growth in the TWA BDs (2M1207A, SSPM1102) remains largely unknown. (5) A Bayesian analysis shows thatmean (log[Mdisk/M∗]) = −2.4, roughly constant all the way from intermediate-mass stars to VLMS/BDs, and (6) thedisk mass in close solar-type Taurus binaries is significantly lower than in singles (by a factor of 10), while that inwide solar-type Taurus binaries is closer to that in singles (lower by a factor of 3). (7) We discuss the implications forplanet formation, and for the dependence of M on M∗.

Accepted by ApJ


B- and A-Type Stars in the Taurus-Auriga Star Forming Region

Kunal P. Mooley1, Lynne A. Hillenbrand1, Luisa M. Rebull2, Deborah L. Padgett2 and Gillian R.

Knapp3

1 Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., MC 249-17, Pasadena, CA91125, USA2 Spitzer Science Center, California Institute of Technology, Pasadena, CA, USA

36



3 Department of Astrophysics, Princeton University, Princeton, NJ, USA

E-mail contact: kunal at astro.caltech.edu

We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex,a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigateseveral sets of possible O, B and early A spectral class members. The first is a group of stars for which mid-infraredimages show bright nebulae, all of which can be associated with stars of spectral type B. The second group consists ofearly-type stars compiled from (i) literature listings in SIMBAD; (ii) B stars with infrared excesses selected from theSpitzer Space Telescope survey of the Taurus cloud; (iii) magnitude- and color-selected point sources from the 2MASS;and (iv) spectroscopically identified early-type stars from the SDSS coverage of the Taurus region. We evaluated starsfor membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallacticdistances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. Forselected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the resultswith the observed spectral energy distributions to further test the plausibility of physical association of the B starswith the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445(HD 28929), τ Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doublingthe number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources includingHD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though notsecure, members.

Accepted by ApJ


X-ray properties of the young open clusters HM1 and IC2944/2948

Yael Naze1, Gregor Rauw1, Hugues Sana2 and Michael F. Corcoran3

1 Dept AGO, Univ of Liege2 Univ. of Amsterdam3 GSFC

E-mail contact: naze at astro.ulg.ac.be

Using XMM data, we study for the first time the X-ray emission of HM1 and IC2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Mostmassive stars in both clusters display the usual high-energy properties of that type of objects, though with log(Lx/Lbol)apparently lower in HM1 than in IC2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the twoWolf-Rayet stars show contrasting behaviors: WR89 is extremely bright, but much softer than WR87. It remains tobe seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC2944/2948, theX-ray sources concentrate around HD101205; a group of massive stars to the north of this object is isolated, suggestingthat there exist two subclusters in the field-of-view.

Accepted by Astron. and Astroph.


The Spatial Distribution of Organics toward the High-Mass YSO NGC 7538 IRS9

Karin I. Oberg1, Mavis D. Boamah2, Edith C. Fayolle3, Robin T. Garrod4, Claudia J. Cyganowski5

and Floris van der Tak6

1 Department of Chemistry, University of Virginia, USA2 Wellesley College, USA3 Leiden Observatory, Leiden University, The Netherlands4 Center for Radiophysics and Space Research, Cornell University, USA5 Harvard-Smithsonian Center for Astrophysics, USA6 Kapteyn Astronomical Institute, University of Groningen, The Netherlands

37



E-mail contact: oberg at virginia.edu

Complex molecules have been broadly classified into three generations dependent on the mode of formation and therequired formation temperature (<25, 25–100 K, and >100 K). Around massive young stellar objects (MYSOs), icygrain mantles and gas are exposed to increasingly higher temperatures as material accretes from the outer envelope intoward the central hot region. The combination of this temperature profile and the generational chemistry should resultin a changing complex molecular composition with radius around MYSOs. We combine IRAM 30m and SubmillimeterArray observations to explore the spatial distribution of organic molecules around the high-mass young stellar objectNGC 7538 IRS9, whose weak complex molecule emission previously escaped detection. We find that emission fromN-bearing organics and CH3OH present substantial increases in emission around 8000 AU and R<3000 AU, whileunsaturated O-bearing molecules and hydrocarbons do not. The increase in line flux for some complex molecules inthe envelope, around 8000 AU or 25 K, is consistent with recent model predictions of an onset of complex ice chemistryat 20–30 K. The emission increase for many of the same molecules at R<3000 AU suggests the presence of a weak hotcore, where thermal ice evaporation and hot gas-phase reactions drive the chemistry. Complex organics thus form at allradii and temperatures around this protostar, but the composition changes dramatically as the temperature increases,which is used together with an adapted gas-grain astrochemical model to constrain the chemical generation(s) to whichdifferent classes of molecules belong.

Accepted by ApJ


Growth of a Protostar and a Young Circumstellar Disk with High Mass Accretion Rateonto the Disk

Takuya Ohtani and Toru Tsuribe

Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho,Toyonaka, Osaka 560-0043, Japan

E-mail contact: ohtani at vega.ess.sci.osaka-u.ac.jp

The growing process of both a young protostar and a circumstellar disk is investigated. Viscous evolution of a diskaround a single star is considered with a model where a disk increases its mass by dynamically accreting envelopeand simultaneously loses its mass via viscous accretion onto the central star. We focus on the circumstellar disk withhigh mass accretion rate onto the disk M = 8.512c3s/G as a result of dynamical collapse of rotating molecular cloudcore. We study the origin of the surface density distribution and the origin of the disk-to-star mass ratio by means ofnumerical calculations of unsteady viscous accretion disk in one-dimensional axisymmetric model. It is shown that theradial profiles of the surface density Σ, azimuthal velocity vφ, and mass accretion rate M in the inner region approachto the quasi-steady state. Profile of the surface density distribution in the quasi-steady state is determined as a resultof angular momentum transport rather than its original distribution of angular momentum in the cloud core. It is alsoshown that the disk mass becomes larger than the central star in the long time limit as long as temporary constantmass flux onto the disk is assumed. After the mass infall rate onto the disk declines owing to the depletion of theparent cloud core, the disk-to-star mass ratio Mdisk/M∗ decreases. The disk-to-star mass ratio becomes smaller thanunity after t > 105 yr and t > 106 yr from the beginning of the accretion phase in the case with α0 = 1 and 0.1,respectively, where α0 is the constant part of viscous parameter. In the case with α0 ≤ 10−2, Mdisk/M∗ is still largerthan unity at 2 Myr from the beginning of the accretion phase.

Accepted by PASJ


The Fate of Planetesimals in Turbulent Disks with Dead Zones. I. The TurbulentStirring Recipe

Satoshi Okuzumi1,2,3 and Chris W. Ormel4,5

1 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-85512 Department of Physics, Nagoya University, Nagoya, Aichi 464-8602, Japan3 JSPS Superlative Research Fellow4 Astronomy Department, University of California, Berkeley, CA 94720, USA

38



5 Hubble Fellow

E-mail contact: okuzumi at geo.titech.ac.jp

Turbulence in protoplanetary disks affects planet formation in many ways. While small dust particles are mainlyaffected by the aerodynamical coupling with turbulent gas velocity fields, planetesimals and larger bodies are moreaffected by gravitational interaction with gas density fluctuations. For the latter process, a number of numericalsimulations have been performed in recent years, but a fully parameter-independent understanding has not been yetestablished. In this study, we present simple scaling relations for the planetesimal stirring rate in turbulence driven bymagnetorotational instability (MRI), taking into account the stabilization of MRI due to Ohmic resistivity. We beginwith order-of-magnitude estimates of the turbulence-induced gravitational force acting on solid bodies and associateddiffusion coefficients for their orbital elements. We then test the predicted scaling relations using the results of recentOhmic-resistive MHD simulations by Gressel et al. We find that these relations successfully explain the simulationresults if we properly fix order-of-unity uncertainties within the estimates. We also update the saturation predictor forthe density fluctuation amplitude in MRI-driven turbulence originally proposed by Okuzumi & Hirose. Combination ofthe scaling relations and saturation predictor allows to know how the turbulent stirring rate of planetesimals dependson disk parameters such as the gas column density, distance from the central star, vertical resistivity distribution,and net vertical magnetic flux. In Paper II, we apply our recipe to planetesimal accretion to discuss its viability inturbulent disks.

Accepted by ApJ


The fate of planetesimals in turbulent disks with dead zones. II. Limits on the viabilityof runaway accretion

C.W. Ormel1 and Satoshi Okuzumi2,3

1 Astronomy Department, University of California, Berkeley, CA 94720, USA2 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-85513 Department of Physics, Nagoya University, Nagoya, Aichi 464-8602, Japan

E-mail contact: ormel at astro.berkeley.edu

A critical phase in the standard model for planet formation is the runaway growth phase. During runaway growthbodies in the 0.1–100 km size range (planetesimals) quickly produce a number of much larger seeds. The runawaygrowth phase is essential for planet formation as the emergent planetary embryos can accrete the leftover planetesimalsat large gravitational focusing factors. However, torques resulting from turbulence-induced density fluctuations mayviolate the criterion for the onset of runaway growth, which is that the magnitude of the planetesimals’ random(eccentric) motions are less than their escape velocity. This condition represents a more stringent constraint thanthe condition that planetesimals survive their mutual collisions. To investigate the effects of MRI turbulence on theviability of the runaway growth scenario, we apply our semi-analytical recipes of Paper I, which we augment by acoagulation/fragmentation model for the dust component. We find that the surface area-equivalent abundance of 0.1µm particles is reduced by factors 102–103, which tends to render the dust irrelevant to the turbulence. We express theturbulent activity in the midplane regions in terms of a size srun above which planetesimals will experience runawaygrowth. We find that srun is mainly determined by the strength of the vertical net field that threads the disks andthe disk radius. At disk radii beyond 5 AU, srun becomes larger than ∼100 km and the collision times among thesebodies longer than the duration of the nebula phase. Our findings imply that the classical, planetesimal-dominated,model for planet formation is not viable in the outer regions of a turbulent disk.

Accepted by ApJ


Reaction of Massive Clusters to Gas Expulsion - The cluster density dependence

Susanne Pfalzner1 and Thomas Kaczmarek1

1 Max-Planck Institut for Radioastronomy, Auf dem Huegel 69, 53121 Bonn, Germany

E-mail contact: spfalzner at mpifr.de

39



The expulsion of the unconverted gas at the end of the star formation process potentially leads to the expansionof the just formed stellar cluster and membership loss. The degree of expansion and mass loss depends largely onthe star formation efficiency and scales with the mass and size of the stellar group as long as stellar interactionscan be neglected. We investigate under which circumstances stellar interactions between cluster members becomeso important that the fraction of bound stars after gas expulsion is significantly altered. The Nbody6 code is usedto simulate the cluster dynamics after gas expulsion for different SFEs. Concentrating on the most massive clustersobserved in the Milky Way, we test to what extend the results depend on the model, i.e. stellar mass distribution,stellar density profile etc., and the cluster parameters, such as cluster density and size.We find that stellar interactionsare responsible for up to 20% mass loss in the most compact massive clusters in the Milky Way, making ejectionsthe prime mass loss process in such systems. Even in the loosely bound OB associations stellar interactions areresponsible for at least ∼ 5% mass loss. The main reason why the importance of encounters for massive clusters hasbeen largely overlooked is the often used approach of a single-mass representation instead of a realistic distributionfor the stellar masses. The density-dependence of the encounter-induced mass loss is shallower than expected becauseof the increasing importance of few-body interactions in dense clusters compared to sparse clusters where 2-bodyencounters dominate.

Accepted by A&A


Spokes cluster: The search for the quiescent gas

Jaime E. Pineda1,2 and Paula S. Teixeira3,4

1 European Southern Observatory (ESO), Garching, Germany2 UK ARC Node, Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester,Manchester, M13 9PL, UK3 Universitat Wien, Institut fur Astrophysik, Turkenschanzstrasse 17, 1180 Vienna, Austria4 Laboratorio Associado Instituto D. Luiz-SIM, Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal

E-mail contact: jaime.e.pineda at gmail.com

Context. Understanding the role of turbulent and thermal fragmentation is one of the most important current questionsof star formation. To better understand the process of star and cluster formation, we need to study in detail the physicalstructure and properties of the parental molecular cloud. In particular, it is important to understand the fragmentationprocess itself; this may be regulated by thermal pressure, magnetic fields, and/or turbulence. The targeted region, theSpokes cluster, or NGC 2264D, is a rich protostellar cluster where previous N2H

+(1–0) observations of its dense corespresented linewidths consistent with supersonic turbulence. However, the fragmentation of the most massive of thesecores appears to have a scale length consistent with that of the thermal Jeans length, suggesting that turbulence wasnot dominant.Aims. These two results (derived from N2H

+(1–0) observations and measurements of the spatial separations ofthe protostars) probe different density regimes. Our aim is to determine if there is subsonic or less-turbulent gas(than previously reported) in the Spokes cluster when probing higher densities, which would reconcile both previousobservational results. To study denser gas it is necessary to carry out observations using transitions with a highercritical density to directly measure its kinematics.Methods. We present APEX N2H

+(3–2) and N2D+(3–2) observations of the NGC2264-D region to measure the

linewidths and the deuteration fraction of the higher density gas. The critical densities of the selected transitions aremore than an order of magnitude higher than that of N2H

+(1–0).Results. We find that the N2H

+(3–2) and N2D+(3–2) emission present significantly narrower linewidths than the

emission from N2H+(1–0) for most cores. In two of the spectra, the nonthermal component is close (within 1-σ) to the

sound speed. In addition, we find that the three spatially segregated cores, for which no protostar had been confirmedshow the highest levels of deuteration.Conclusions. These results show that the higher density gas, probed with N2H

+ and N2D+(3–2), reveals more quiescent

gas in the Spokes cluster than previously reported. More high-angular resolution interferometric observations usinghigh-density tracers are needed to truly assess the kinematics and substructure within NGC2264-D.

Accepted by A&A

http://uk.arxiv.org/pdf/1305.3329

40


http://uk.arxiv.org/pdf/1305.3329

Explaining millimeter-sized particles in brown dwarf disks

P. Pinilla1, T. Birnstiel2,3, M. Benisty4, L. Ricci5, A. Natta6, C. P. Dullemond1, C. Dominik7,8 and L.

Testi9,10

1 Universitat Heidelberg, Zentrum fur Astronomie, Institut fur Theoretische Astrophysik, Germany2 Harvard-Smithsonian Center for Astrophysics, USA3 Excellence Cluster Universe, Garching, Germany4 Laboratoire d’Astrophysique, Observatoire de Grenoble, France5 California Institute of Technology, USA6 INAF - Osservatorio Astrofisico di Arcetri, Italy7 School of Cosmic Physics, Dublin Institute for Advanced Studies, Ireland8 Astronomical Institute ’Anton Pannekoek’, University of Amsterdam, The Netherlands9 Department of Astrophysics/IMAPP, Radboud University Nijmegen, The Netherlands10 European Southern Observatory, Garching, Germany

E-mail contact: pinilla at uni-heidelberg.de

Context. Planets have been detected around a variety of stars, including low-mass objects, such as brown dwarfs.However, such extreme cases are challenging for planet formation models. Recent sub-millimeter observations of disksaround brown dwarf measured low spectral indices of the continuum emission that suggest that dust grains grow tomm-sizes even in these very low mass environments.Aims. To understand the first steps of planet formation in scaled-down versions of T-Tauri disks, we investigate thephysical conditions that can theoretically explain the growth from interstellar dust to millimeter-sized grains in disksaround brown dwarf.Methods. We modeled the evolution of dust particles under conditions of low-mass disks around brown dwarfs. Weused coagulation, fragmentation and disk-structure models to simulate the evolution of dust, with zero and non-zeroradial drift. For the non-zero radial drift, we considered strong inhomogeneities in the gas surface density profile thatmimic long-lived pressure bumps in the disk. We studied different scenarios that could lead to an agreement betweentheoretical models and the spectral slope found by millimeter observations.Results. We find that fragmentation is less likely and rapid inward drift is more significant for particles in brown dwarfdisks than in T-Tauri disks. We present different scenarios that can nevertheless explain millimeter-sized grains. Asan example, a model that combines the following parameters can fit the millimeter fluxes measured for brown dwarfdisks: strong pressure inhomogeneities of ∼ 40% of amplitude, a small radial extent ∼ 15 AU, a moderate turbulencestrength αturb = 10−3, and average fragmentation velocities for ices vf = 10 m s−1.

Accepted by A&A


HST/WFC3 Imaging of Protostellar Jets in Carina: [Fe II] Emission Tracing MassiveJets from Intermediate Mass Protostars

Megan Reiter1 and Nathan Smith1

1 University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721-0065, USA

E-mail contact: mreiter at as.arizona.edu

We present narrowband Wide Field Camera 3 (WFC3)-UVIS and -IR images of four externally irradiated protostellarjets in the Carina nebula: HH 666, HH 901, HH 902, and HH 1066. These massive jets are unusual because theyare bathed in UV radiation from dozens of nearby O-type stars, but despite the strong incident ionizing radiation,portions of the jet remain neutral. Near-IR [Fe II] images reveal dense, neutral gas that was not seen in previous studiesof Hα emission. We show that near-IR [Fe II] emitting gas must be self-shielded from Lyman continuum photons,regardless of its excitation mechanism (shocks, FUV radiation, or both). High densities are required for the survivalof Fe+ amid the strong Lyman continuum luminosity from Tr14, raising estimates of the mass-loss rates by an order ofmagnitude. Higher jet mass-loss rates require higher accretion rates onto their driving protostars, implying that thesejets are driven by intermediate-mass (∼ 2− 8 M⊙) stars. Indeed, the IR driving sources of two of these outflows haveluminosities that require intermediate-mass protostars (the other two are so deeply embedded that their luminosityis uncertain). All four of these HH jets are highly collimated, with opening angles of only a few degrees, similar to

41


those observed in low-mass protostars. We propose that these jets reflect essentially the same outflow phenomenonseen in wide-angle molecular outflows associated with intermediate- and high-mass protostars, but that the collimatedatomic jet core is irradiated and rendered observable in the harsh radiative environment of the Carina nebula. Inmore quiescent environments, this atomic core remains invisible, and outflows traced by shock-excited molecules inthe outflow cavity give the impression that these outflows have a wider opening angle. Thus, the externally irradiatedjets in Carina constitute a new view of collimated jets from intermediate-mass protostars, and offer strong additionalevidence that stars up to at least ∼ 8 M⊙ form by the same accretion mechanisms as low-mass stars.

Accepted by MNRAS


Understanding the origin of the [OI] low-velocity component from T Tauri stars

Elisabetta Rigliaco1, Ilaria Pascucci1, Uma Gorti2,3, Suzan Edwards4 and David Hollenbach2

1 Department of Planetary Science - University of Arizona - 1629 E. University Blvd, 85721 Tucson, AZ, USA2 Seti Institute, Mountain View, CA 94043, USA3 NASA Ames research center, Moffet Field, CA, USA4 Astronomy Department, Smith College, Northampton, MA 01063, USA

E-mail contact: rigliaco at lpl.arizona.edu

The formation time, masses, and location of planets are strongly impacted by the physical mechanisms that disperseprotoplanetary disks and the timescale over which protoplanetary material is cleared out. Accretion of matter onto thecentral star, protostellar winds/jets, magnetic disk winds, and photoevaporative winds operate concurrently. Hence,disentangling their relative contribution to disk dispersal requires identifying diagnostics that trace different star-diskenvironments. Here we analyze the low velocity component (LVC) of the Oxygen optical forbidden lines, which isfound to be blueshifted by a few km/s with respect to the stellar velocity. We find that the [O i] LVC profiles aredifferent from those of [Ne ii] at 12.81µm and CO at 4.7µm lines pointing to different origins for these gas lines. Wereport a correlation between the luminosity of the [O i] LVC and the accretion luminosity (Lacc). We do not find anycorrelation with the X-ray luminosity, while we find that the higher is the stellar FUV luminosity, the higher is theluminosity of the [O i] LVC. In addition, we show that the [O i]6300A/5577A ratio is low (ranging between 1 and 8).These findings favor an origin of the [O i] LVC in a region where OH is photodissociated by stellar FUV photons andargue against thermal emission from an X-ray-heated layer. Detailed modeling of two spectra with the highest S/Nand resolution shows that there are two components within the LVC: a broad, centrally peaked component that can beattributed to gas arising in a warm disk surface in Keplerian rotation (with FWHM between ∼40 and ∼60 km/s), anda narrow component (with FWHM∼10 km/s and small blueshifts of ∼2 km/s) that may arise in a cool (<∼1,000 K)molecular wind.

Accepted by ApJ


Measuring Protoplanetary Disk Accretion with H I Pfund beta

Colette Salyk1, Gregory J. Herczeg2, Joanna M. Brown3, Geoffrey A. Blake4, Klaus M. Pontoppidan5

and Ewine F. van Dishoeck6,7

1 National Optical Astronomy Observatory, 950 N Cherry Ave, Tucson, AZ 85719, USA2 The Kavli Institute for Astronomy and Astrophysics at Peking University, Yi He Yuan Lu 5, Hai Dian Qu, Beijing100871, China3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA4 Division of Geological & Planetary Sciences, Mail Code 150-21, California Institute of Technology, Pasadena, CA91125, USA5 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA6 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands7 Max-Planck-Institute fur Extraterrestriche Physik, Giessenbachstrasse 1, D-85748 Garching, Germany

E-mail contact: csalyk at noao.edu

42



In this work, we introduce the use of H I Pfund β (Pfβ; 4.6538 µm) as a tracer of mass accretion from protoplanetarydisks onto young stars. Pfβ was serendipitously observed in NIRSPEC and CRIRES surveys of CO fundamentalemission, amounting to a sample size of 120 young stars with detected Pfβ emission. Using a subsample of diskswith previously measured accretion luminosities, we show that Pfβ line luminosity is well correlated with accretionluminosity over a range of at least three orders of magnitude. We use this correlation to derive accretion luminositiesfor all 120 targets, 65 of which are previously unreported in the literature. The conversion from accretion luminosityto accretion rate is limited by the availability of stellar mass and radius measurements; nevertheless, we also reportaccretion rates for 67 targets, 16 previously unmeasured. Our large sample size and our ability to probe high extinctionvalues allow for relatively unbiased comparisons between different types of disks. We find that the transitional disks inour sample have lower than average Pfβ line luminosities, and thus accretion luminosities, at a marginally significantlevel. We also show that high Pfβ equivalent width is a signature of transitional disks with high inner disk gas/dustratios. In contrast, we find that disks with signatures of slow disk winds have Pfβ luminosities comparable to thoseof other disks in our sample. Finally, we investigate accretion rates for stage I disks, including significantly embeddedtargets. We find that stage I and stage II disks have statistically indistinguishable Pfβ line luminosities, implyingsimilar accretion rates, and that the accretion rates of stage I disks are too low to be consistent with quiescent accretion.Our results are instead consistent with both observational and theoretical evidence that stage I objects experienceepisodic, rather than quiescent, accretion.



Direct detection of the tertiary component in the massive multiple HD 150 136 withVLTI

J. Sanchez-Bermudez1,2, R. Schodel1, A. Alberdi1, R. H. Barba3, C. A. Hummel2, J. Maız Apellaniz1

and J.-U. Pott4

1 Instituto de Astrofsica de Andaluca (CSIC), Glorieta de la Astronoma S/N, 18008 Granada, Spain2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany3 Departamento de Fısica, Universidad de la Serena, Benavente 980, 204000 La Serena, Chile4 Max-Planck-Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany

E-mail contact: sanchezj at eso.org

Massive stars are of fundamental importance for almost all aspects of astrophysics, but there still exist large gaps inour understanding of their properties and formation because they are rare and therefore distant. It has been foundthat most O-stars are multiples. HD 150 136 is the nearest system to Earth with > 100M⊙, and provides a uniqueopportunity to study an extremely massive system. Recently, evidence for the existence of a third component in HD150 136, in addition to the tight spectroscopic binary that forms the main component, was found in spectroscopicobservations. Our aim was to image and obtain astrometric and photometric measurements of this component usinglong baseline optical interferometry to further constrain the nature of this component. We observed HD 150 136 withthe near-infrared instrument AMBER attached to the ESO VLT Interferometer. The recovered closure phases arerobust to systematic errors and provide unique information on the source asymmetry. Therefore, they are of crucialrelevance for both image reconstruction and model fitting of the source structure. The third component in HD 150136 is clearly detected in the high-quality data from AMBER. It is located at a projected angular distance of 7.3mas, or about 13 AU at the line-of-sight distance of HD 150 136, at a position angle of 209 degrees East of North,and has a flux ratio of 0.25 with respect to the inner binary. We resolved the third component of HD 150 136 in J,H and K filters. The luminosity and color of the tertiary agrees with the predictions and shows that it is also anO main-sequence star. The small measured angular separation indicates that the tertiary may be approaching theperiastron of its orbit. These results, only achievable with long baseline near infrared interferometry, constitute thefirst step towards the understanding of the massive star formation mechanisms.

Accepted by A & A


43



Evolution and excitation conditions of outflows in high-mass star-forming regions

A. Sanchez-Monge1, A. Lopez-Sepulcre2, R. Cesaroni1, C.M. Walmsley1,3, C. Codella1, M.T. Beltran1,

M. Pestalozzi4 and S. Molinari4

1 Osservatorio Astrofisico di Arcetri, INAF, Largo Enrico Fermi 5, I-50125, Firenze, Italy2 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno-ble, F-380413 Dublin Institute for Advanced Studies (DIAS), 31 Fitzwilliam Place, Dublin 2, Ireland4 INAF - Istituto di Astrofisica e Planetologia Spaziali, Via Fosso de Cavaliere 100, I-00133, Roma, Italy

E-mail contact: asanchez at arcetri.astro.it

Theoretical models suggest that massive stars form via disk-mediated accretion, in a similar fashion to low-mass stars.In this scenario, bipolar outflows ejected along the disk axis play a fundamental role, and their study can help tocharacterize the different evolutionary stages involved in the formation of a high-mass star. A recent study towardmassive molecular outflows has revealed a decrease of the SiO line intensity as the object evolves. The present studyaims at characterizing the variation of the molecular outflow properties with time, and at studying the SiO excitationconditions in outflows associated with high-mass young stellar objects (YSOs). We used the IRAM 30-m telescope onPico Veleta (Spain) to map 14 high-mass star-forming regions in the SiO (2–1), SiO (5–4) and HCO+ (1–0) lines, whichtrace the molecular outflow emission. The FTS backend, covering a total frequency range of ∼15 GHz, allowed us tosimultaneously map several dense gas (e. g., N2H

+, C2H, NH2D, H13CN) and hot core (CH3CN) tracers. We usedthe Hi-GAL data to improve the previous spectral energy distributions, and obtain a more accurate dust envelopemass and bolometric luminosity for each source. We calculated the luminosity-to-mass ratio, which is believed to bea good indicator of the evolutionary stage of the YSO. We detect SiO and HCO+ outflow emission in all the fourteensources, and bipolar structures in six of them. The outflow parameters are similar to those found toward other massiveYSOs with luminosities 103–104 L⊙. We find an increase of the HCO+ outflow energetics as the object evolve, anda decrease of the SiO abundance with time, from 10−8 to 10−9. The SiO (5–4) to (2–1) line ratio is found to be lowat the ambient gas velocity, and increases as we move to red/blue-shifted velocities, indicating that the excitationconditions of the SiO change with the velocity of the gas. In particular, the high-velocity SiO gas component seemsto arise from regions with larger densities and/or temperatures, than the SiO emission at the ambient gas velocity.The properties of the SiO and HCO+ outflow emission suggest a scenario in which SiO is largely enhanced in the firstevolutionary stages, probably due to strong shocks produced by the protostellar jet. As the object evolves, the powerof the jet would decrease and so does the SiO abundance. During this process, however, the material surrounding theprotostar would have been been swept up by the jet, and the outflow activity, traced by entrained molecular material(HCO+), would increase with time.



Properties of dense cores in clustered massive star-forming regions at high angularresolutions

A. Sanchez-Monge1,2, A. Palau3, F. Fontani1, G. Busquet4, C. Juarez3,2, R. Estalella2, J.C. Tan5, I.

Sepulveda2, P.T.P. Ho6,7, Q. Zhang7 and S. Kurtz8

1 Osservatorio Astrofisico di Arcetri, INAF, Largo Enrico Fermi 5, I-50125, Firenze, Italy2 Dpt d’Astronomia i Meteorologia (IEEC-UB), ICC, Universitat de Barcelona, Marti i Franques 1, E-08028, Barcelona,Spain3 Institut de Ciencies de l’Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C-5p, E-08193, Bellaterra,Spain4 INAF - Istituto di Astrofisica e Planetologia Spaziali, Via Fosso de Cavaliere 100, I-00133, Roma, Italy5 Dpt of Astronomy and Physics, University of Florida, Gainesville, FL 32611, USA6 Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan7 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA8 Centro de Radioastronomia y Astrofisica, UNAM, P.O. Box 3-72, 58090, Morelia, Mexico

E-mail contact: asanchez at arcetri.astro.it

44


We aim at characterising dense cores in the clustered environments associated with intermediate/high-mass star-forming regions. For this, we present an uniform analysis of Very Large Array NH3 (1,1) and (2,2) observationstowards a sample of 15 intermediate/high-mass star-forming regions, where we identify a total of 73 cores, classifythem as protostellar, quiescent starless, or perturbed starless, and derive some physical properties. The average sizesand ammonia column densities of the total sample are ∼ 0.06 pc and ∼ 1015 cm−2, respectively, with no significantdifferences between the starless and protostellar cores, while the linewidth and rotational temperature of quiescentstarless cores are smaller, ∼ 1.0 km s−1 and 16 K, than linewidths and temperatures of protostellar (∼ 1.8 km s−1 and21 K), and perturbed starless (∼ 1.4 km s−1 and 19 K) cores. Such linewidths and temperatures for these quiescentstarless cores in the surroundings of intermediate/high-mass stars are still significantly larger than the typical linewidthsand rotational temperatures measured in starless cores of low-mass star-forming regions, implying an important non-thermal component. We confirm at high angular resolutions (spatial scales ∼ 0.05 pc) the correlations previouslyfound with single-dish telescopes (spatial scales >∼0.1 pc) between the linewidth and the rotational temperature of thecores, as well as between the rotational temperature and the linewidth with respect to the bolometric luminosity. Inaddition, we find a correlation between the temperature of each core and the incident flux from the most massive starin the cluster, suggesting that the large temperatures measured in the starless cores of our sample could be due toheating from the nearby massive star. A simple virial equilibrium analysis seems to suggest a scenario of a self-similar,self-graviting, turbulent, virialised hierarchy of structures from clumps (∼ 0.1–10 pc) to cores (∼ 0.05 pc). A closerinspection of the dynamical state taking into account external pressure effects, reveal that relatively strong magneticfield support may be needed to stabilise the cores, or that they are unstable and thus on the verge of collapse.

Accepted by Monthly Notices of the Royal Astronomical Society


Multiwavelength interferometric observations and modeling of circumstellar disks

A.A. Schegerer1,2, T. Ratzka3, P.A. Schuller4, S. Wolf5, L. Mosoni6, Ch. Leinert2

1 Bundesamt fur Strahlenschutz, Fachbereich fur Strahlenschutz und Gesundheit, Ingolstadter Landstrae 1, 85764Neuherberg, Germany2 Max-Planck-Institut fur Astronomie, Konigstuhl 17, 69117 Heidelberg, Germany3 Ludwig-Maximilians-Universitat, Universitats-Sternwarte Munchen, Scheinerstraße 1, 81679 Munchen, Germany4 Universitat zu Koln, I. Physikalisches Institut, Zulpicher Straße 77, 50937 Koln, Germany5 Universitat Kiel, Institut fur Theoretische Physik und Astrophysik, Leibnizstraße 15, 24098 Kiel, Germany6 MTA Research Center for Astronomy and Earth Sciences, Konkoly Thege Miklos Astronomical Institute, 1525Budapest, Hungary

E-mail contact: aschegerer at bfs.de

We investigate the structure of the innermost region of three circumstellar disks around pre-main sequence stars HD142666, AS 205 N, and AS 205 S. We determine the inner radii of the dust disks and, in particular, search for transitionobjects where dust has been depleted and inner disk gaps have formed at radii of a few tenths of AU up to several AU.We performed interferometric observations with IOTA, AMBER, and MIDI in the infrared wavelength ranges 1.6 – 2.5µm and 8 – 13 µm with projected baseline lengths between 25 m and 102 m. The data analysis was based on radiativetransfer simulations in 3D models of young stellar objects (YSOs) to reproduce the spectral energy distribution andthe interferometric visibilities simultaneously. Accretion effects and disk gaps could be considered in the modelingapproach. Results from previous studies restricted the parameter space. The objects of this study were spatiallyresolved in the infrared wavelength range using the interferometers. Based on these observations, a disk gap could befound for the source HD 142666 that classifies it as transition object. There is a disk hole up to a radius of Rin = 0.30AU and a (dust-free) ring between 0.35 AU and 0.80 AU in the disk of HD 142666. The classification of AS 205 asa system of classical T Tauri stars could be confirmed using the canonical model approach, i.e., there are no hints ofdisk gaps in our observations.

Accepted by A&A


45



Interstellar Detection of c-C3D2

Silvia Spezzano1, Sandra Brunken1, Peter Schilke1, Paola Caselli2, Karl M. Menten3, Michael C.

McCarthy4, Luca Bizzocchi5, Sandra Trenivo-Morales6, Yuri Aikawa7 and Stephan Schlemmer1

1 I. Physikalisches Institut, Universitat zu Koln, Zulpicher Str. 77, 50937 Koln, Germany2 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK3 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany4 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, and School of Engineering &Applied Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138, USA5 Centro de Astronomia e Astrofisica, Observ. Astronomico de Lisboa Tapada da Ajuda, 1349-018 Lisboa, Portugal6 IRAM, 18012, Granada, Spain7 Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501, Japan

E-mail contact: spezzano at ph1.uni-koeln.de

We report the first interstellar detection of c-C3D2. The doubly deuterated cyclopropenylidene, a carbene, has beendetected toward the starless cores TMC-1C and L1544 using the IRAM 30m telescope. The JKa,Kc

= 30,3 − 21,2,31,3 − 20,2, and 22,1 − 11,0 transitions of this species have been observed at 3 mm in both sources. The expected 1:2intensity ratio has been found in the 30,3 - 21,2 and 31,3 - 20,2 lines, belonging to the para and ortho species respectively.We also observed lines of the main species, c-C3H2, the singly deuterated c-C3HD, and the species with one 13C offof the principal axis of the molecule, c-H13CC2H. The lines of c-C3D2 have been observed with high signal to noiseratio, better than 7.5σ in TMC-1C and 9σ in L1544. The abundance of doubly deuterated cyclopropenylidene withrespect to the normal species is found to be (0.4 - 0.8)% in TMC-1C and (1.2 - 2.1)% in L1544. The deuteration ofthis small hydrocarbon ring is analysed with a comprehensive gas-grain model, the first including doubly deuteratedspecies. The observed abundances of c-C3D2 can be explained solely by gas-phase processes, supporting the idea thatc-C3H2 is a good indicator of gas-phase deuteration.

Accepted by ApJ Letters


A Semi-Analytical Description for the Formation and Gravitational Evolution of Pro-toplanetary Disks

Sanemichi Z. Takahashi1,2, Shu-ichiro Inutsuka1, and Masahiro N. Machida3

1 Department of Physics, Nagoya University, Furocho, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan2 Department of Physics, Kyoto University, Oiwakecho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan3 Department of Earth and Planetary Science, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan

E-mail contact: takahashi.sanemichi at a.mbox.nagoya-u.ac.jp

We investigate the formation process of self-gravitating protoplanetary disks in unmagnetized molecular clouds. Theangular momentum is redistributed by the action of gravitational torques in the massive disk during its early formation.We develop a simplified one-dimensional accretion disk model that takes into account the infall of gas from the envelopeonto the disk and the transfer of angular momentum in the disk with an effective viscosity. First we evaluate the gasaccretion rate from the cloud core onto the disk by approximately estimating the effects of gas pressure and gravityacting on the cloud core. We formulate the effective viscosity as a function of the Toomre Q parameter that measuresthe local gravitational stability of the rotating thin disk. We use a function for viscosity that changes sensitively withQ when the disk is gravitationally unstable. We find a strong self-regulation mechanism in the disk evolution. Duringthe formation stage of protoplanetary disks, the evolution of the surface density does not depend on the other detailsof the modeling of effective viscosity, such as the prefactor of the viscosity coefficient. Next, to verify our model, wecompare the time evolution of the disk calculated with our formulation with that of three-dimensional hydrodynamicalsimulations. The structures of the resultant disks from the one-dimensional accretion disk model agree well with thoseof the three-dimensional simulations. Our model is a useful tool for the further modeling of chemistry, radiativetransfer, and planet formation in protoplanetary disks.

Accepted by ApJ


46



The relation of H2CO, 12CO, and 13CO in molecular clouds

Xin. Di. Tang1,2, Jarken. Esimbek1,3, Jian. Jun. Zhou1,3, Gang. Wu1,3, Wei. Guang. Ji1,2, and Daniel.

Okoh1,4

1 Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, PR China2 Graduate University of the Chinese Academy of Sciences, Beijing 100080, PR China3 Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Urumqi 830011, PR China4 Physics & Astronomy Department, University of Nigeria, Nsukka 410001, Nigeria

E-mail contact: tangxindi at xao.ac.cn

Aims. We seek to understand how the 4.8 GHz formaldehyde absorption line is distributed in the MON R2, S156,DR17/L906, and M17/M18 regions. More specifically, we look for the relationship among the H2CO, 12CO, and 13COspectral lines.Methods. The four regions of MON R2 (60′ × 90′), S156 (50′ × 70′), DR17/L906 (40′ × 60′), and M17 /M18 (70′ ×80′) were observed for H2CO (beam 10′), H110α recombination (beam 10′), 6 cm continuum (beam 10′), 12CO (beam1′), and 13CO (beam 1′). We compared the H2CO, 12CO, 13CO, and continuum distributions, and also the spectraline parameters of H2CO, 12CO, and 13CO. Column densities of H2CO, 13CO, and H2 were also estimated.Results. We found out that the H2CO distribution is similar to the 12CO and the 13CO distributions on a largescale. The correlation between the 13CO and the H2CO distributions is better than between the 12CO and H2COdistributions. The H2CO and the 13CO tracers systematically provide consistent views of the dense regions. Theirmaps have similar shapes, sizes, peak positions, and molecular spectra and present similar central velocities and linewidths. Such good agreement indicates that the H2CO and the 13CO arise from similar regions.

Accepted by A&A (551, A28, 2013)


Discovery of Methyl Acetate and Gauche Ethyl Formate in Orion

B. Tercero1, I. Kleiner2, J. Cernicharo1, H.V.L. Nguyen2, A. Lopez1, and G.M. Munoz Caro1

1 Department of Astrophysics, CAB. INTA-CSIC. Crta Torrejon-Ajalvir, km. 4. 28850 Torrejon de Ardoz. Madrid.Spain2 Laboratoire Interuniversitaire des Systemes Atmospheriques, CNRS/IPSL UMR7583 et Universites Paris Diderot etParis Est, 61 av General de Gaulle, 94010, Creteil, France

E-mail contact: terceromb at cab.inta-csic.es

We report on the discovery of methyl acetate, CH3COOCH3, through the detection of a large number of rotationallines from each one of the spin states of the molecule: AA species (A1 or A2), EA species (E1), AE species (E2), EEspecies (E3 or E4). We also report the detection, for the first time in space, of the gauche conformer of ethyl formate,CH3CH2OCOH, in the same source. The trans conformer is also detected for the first time outside the galactic centersource SgrB2. From the derived velocity of the emission of methyl acetate we conclude that it arises mainly from thecompact ridge region with a total column density of (4.2 ± 0.5)× 1015 cm−2. The derived rotational temperature is150 K. The column density for each conformer of ethyl formate, trans and gauche, is (4.5± 1.0)× 1014 cm−2. Theirabundance ratio indicates a kinetic temperature of 135 K for the emitting gas and suggests that gas phase reactionscould participate efficiently in the formation of both conformers in addition to cold ice mantle reactions on the surfaceof dust grains.

Accepted by ApJL


Millimeter Recombination Lines from LkHα 101

C. Thum1, R. Neri2, A. BaezRubio3, and M. Krips2

1 Instituto de Radio Astronomıa Milimetrica, Avenida Divina Pastora 7, Nucleo Central, 18012 Granada, Spain 2

Institut de Radio Astronomie Millimetrique, 300 rue de la Piscine, Dom. Univ. de Grenoble, 38406 Saint Martind’Heres, France

47



3 Centro de Astrobiologıa (CSIC/INTA) Ctra de Torrejon a Ajalvir, km 4, 28850 Torrejon de Ardoz, Madrid Spain

E-mail contact: thum at iram.es

We present new millimeter observations of the ionized wind from the massive young stellar object LkHα101, madewith the IRAM interferometer and 30m telescope. Several recombination lines, including higher order transitions,were detected for the first time at radio wavelengths in this source. From three α-transitions we derive an accuratevalue for the stellar velocity and, for the first time, an unambiguous expansion velocity of the wind which is 55 kms−1, much slower than reported previously, and the mass loss rate is 1.8× 10−6 M⊙ yr−1. The wide band continuumspectra and the interferometer visibilities show that the density of the wind falls off more steeply than compatiblewith constant-velocity expansion. We argue that these properties indicate that the wind is launched from a radiallynarrow region of the circumstellar disk, and we propose that slow speed and a steep density gradient are characteristicproperties of the evolutionary phase where young stars of intermediate and high mass clear away the gaseous compo-nent of their accretion disks.The recombination lines are emitted close to local thermal equilibrium, but the higher order transitions appear sys-tematically broader and weaker than expected, probably due to impact broadening. Finally, we show that LkHα101shares many properties with MWC349, the only other stellar wind source where radio recombination lines have beendetected, some of them masing. We argue that LkHα101 evades masing at millimeter wavelengths because of thedisk’s smaller size and unfavorable orientation. Some amplification may however be detectable at shorter wavelengths.

Accepted by A&A


Modeling the Resolved Disk Around the Class 0 Protostar L1527

John J. Tobin1,8, Lee Hartmann2, Hsin-Fang Chiang3,4, David J. Wilner5, Leslie W. Looney3, Laurent

Loinard6,7, Nuria Calvet2, Paola D’Alessio6

1 National Radio Astronomy Observatory, Charlottesville, VA 22903, USA2 Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA3 Department of Astronomy, University of Illinois, Urbana, IL 61801, USA4 Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii at Manoa, Hilo, HI 96720, USA5 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA6 Centro de Radioastronomıa y Astrofısica, UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacan,Mexico7 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany8 Hubble Fellow

E-mail contact: jtobin at nrao.edu

We present high-resolution sub/millimeter interferometric imaging of the Class 0 protostar L1527 IRS (IRAS 04368+2557)at 870 µm and 3.4 mm from the Submillimeter Array (SMA) and Combined Array for Research in Millimeter As-tronomy (CARMA). We detect the signature of an edge-on disk surrounding the protostar with an observed diameterof 180 AU in the sub/millimeter images. The mass of the disk is estimated to be 0.007 M⊙, assuming opticallythin, isothermal dust emission. The millimeter spectral index is observed to be quite shallow at all the spatial scalesprobed; α ∼ 2, implying a dust opacity spectral index beta ∼ 0. We model the emission from the disk and surroundingenvelope using Monte Carlo radiative transfer codes, simultaneously fitting the sub/millimeter visibility amplitudes,sub/millimeter images, resolved L′ image, spectral energy distribution, and mid-infrared spectrum. The best fittingmodel has a disk radius of R = 125 AU, is highly flared (H ∝ R1.3), has a radial density profile ρ ∝ R−2.5, and hasa mass of 0.0075 M⊙. The scale height at 100 AU is 48 AU, about a factor of two greater than vertical hydrostaticequilibrium. The resolved millimeter observations indicate that disks may grow rapidly throughout the Class 0 phase.The mass and radius of the young disk around L1527 is comparable to disks around pre-main sequence stars; however,the disk is considerably more vertically extended, possibly due to a combination of lower protostellar mass, infall ontothe disk upper layers, and little settling of ∼1 µm-sized dust grains.

Accepted by ApJ


48



Studying the kinematics of the giant star-forming region 30 Doradus. I. The data

S. Torres-Flores1, R. Barba1,2, J. Maız Apellaniz3, M. Rubio4, G. Bosch5, V. Henault-Brunet6, C. J.

Evans7

1 Departamento de Fısica, Universidad de La Serena, Av. Cisternas 1200 Norte, La Serena, Chile2 Instituto de Ciencias Astronomicas, de la Tierra y del Espacio, Casilla 467, 5400 San Juan, Argentina3 Instituto de Astrofısica de Andalucıa-CSIC, Glorieta de la Astronomıa s/n, 18008 Granada, Spain4 Departamento de Astronomıa, Universidad de Chile, Casilla 36-D, Santiago, Chile5 Facultad de Ciencias Astronomicas y Geofısicas, Universidad Nacional de la La Plata, Paseo del Bosque s/n, 1900La Plata, Argentina6 Institute for Astronomy, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK7 UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK

E-mail contact: storres at dfuls.cl

We present high-quality VLT-FLAMES optical spectroscopy of the nebular gas in the giant star-forming region 30Doradus. In this paper, the first of a series, we introduce our observations and discuss the main kinematic featuresof 30 Dor, as revealed by the spectroscopy of the ionized gas in the region. The primary data set consists of regulargrid of nebular observations, which we used to produce a spectroscopic datacube of 30 Dor, centered on the massivestar cluster R136 and covering a field-of-view of 10′ × 10′. The main emission lines present in the datacube are fromHα and [Nii] 6548,6584. The Hα emission-line profile varies across the region from simple single-peaked emission tocomplex, multiple-component profiles, suggesting that different physical mechanisms are acting on the excited gas.To analyse the gas kinematics we fit Gaussian profiles to the observed Hα features. Unexpectedly, the narrowest Hαprofile in our sample lies close to the supernova remnant 30 Dor B. We present maps of the velocity field and velocitydispersion across 30 Dor, finding five previously unclassified expanding structures. These maps highlight the kinematicrichness of 30 Dor (e.g. supersonic motions), which will be analysed in future papers.

Accepted by A&A


The Responses of Magnetically Sub-Critical Cores to Shocks

B. Vaidya1, T.W. Hartquist1 and S.A.E.G. Falle2

1 School of Physics and Astronomy, University of Leeds, Leeds, UK2 Department of Applied Mathematics, University of Leeds, Leeds, UK

E-mail contact: B.Vaidya at leeds.ac.uk

An ideal magnetohydrodynamics (MHD) code with adaptive mesh refinement (AMR) was used to investigate theinteractions of fast-mode shocks with self-gravitating, isothermal cores with mass-to-flux ratios that are somewhatbelow the minimum value required for gravitational collapse. We find that shock focussing produces colliding flowsalong the field lines that generate very high densities, even for relatively weak shocks. Self-gravity plays only a minorrole in determining the highest density that is reached, but it does play a role in the subsequent evolution. Thedensities at comparable times differ by a factor of a few for shocks initially propagating perpendicularly or obliquelyto the magnetic field in the ambient medium.

Accepted by MNRAS


Outflow forces of low mass embedded objects in Ophiuchus: a quantitative comparisonof analysis methods

N. van der Marel1, L.E. Kristensen1,2, R. Visser3, J.C. Mottram1, U.A. Yıldız1, and E.F. van Dishoeck1,4

1 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, the Netherlands2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA3 Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109-1042, USA4 Max-Planck-Institut fur Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany

49



E-mail contact: nmarel at strw.leidenuniv.nl

The outflow force of molecular bipolar outflows is a key parameter in theories of young stellar feedback on theirsurroundings. The focus of many outflow studies is the correlation between the outflow force, bolometric luminosityand envelope mass. However, it is difficult to combine the results of different studies in large evolutionary plots overmany orders of magnitude due to the range of data quality, analysis methods and corrections for observational effectssuch as opacity and inclination. We aim to determine the outflow force for a sample of low luminosity embeddedsources. We will quantify the influence of the analysis method and the assumptions entering the calculation of theoutflow force. We use the James Clerk Maxwell Telescope to map 12CO J = 3 − 2 over 2′ × 2′ regions around 16Class I sources of a well-defined sample in Ophiuchus at 15′′ resolution. The outflow force is then calculated usingseven different methods differing e.g. in the use of intensity-weighted emission and correction factors for inclination.The results from the analysis methods differ from each other by up to a factor of 6, whereas observational propertiesand choices in the analysis procedure affect the outflow force by up to a factor of 4. For the sample of Class Iobjects, bipolar outflows are detected around 13 sources including 5 new detections, where the three non-detectionsare confused by nearby outflows from other sources. When combining outflow forces from different studies, a scatterby up to a factor of 5 can be expected. Although the true outflow force remains unknown, the separation method(separate calculation of dynamical time and momentum) is least affected by the uncertain observational parameters.The correlations between outflow force, bolometric luminosity and envelope mass are further confirmed down to lowluminosity sources.

Accepted by A&A


Systematic Variations of Interstellar Linear Polarization and Growth of Dust Grains

N. V. Voshchinnikov1, H. K. Das2, I. S. Yakovlev1, V. B. Il’in1,3,4

1Sobolev Astronomical Institute, St. Petersburg University, Russia2 Inter-University Center for Astronomy and Astrophysics, Pune, India3Pulkovo Observatory, St. Petersburg, Russia4St. Petersburg State University of Aerospace Instrumentation, St. Petersburg, Russia

E-mail contact: nvv at astro.spbu.ru

A quantitative interpretation of the observed relation between the interstellar linear polarization curve parametersK and λmax characterizing the width and the wavelength of a polarization maximum, respectively, is given. Theobservational data available for 57 stars located in the dark clouds in Taurus, Chamaeleon, around the stars ρ Ophand R CrA are considered. The spheroidal particle model of interstellar dust grains earlier applied to simultaneouslyinterpret the interstellar extinction and polarization curves in a wide spectral range is utilized. The observed trendK ≈ 1.7λmax is shown to be most likely related to a growth of dust grains due to coagulation rather than mantleaccretion. The relation of the parameters K and λmax with an average size of silicate dust grains is discussed.

Accepted by Astronomy Letters (39, 421–431, 2013)

http://arXiv.org/pdf/1303.1033

Unveiling the Evolutionary Sequence from Infalling Envelopes to Keplerian Disks aroundLow-Mass Protostars

Hsi-Wei Yen1,2, Shigehisa Takakuwa2, Nagayoshi Ohashi2,3 and Paul T.P. Ho2,4

1 Institute of Astrophysics, National Taiwan University, Taipei 10617, Taiwan2 Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan3 Subaru Telescope, National Astronomical Observatory of Japan, 650 North Aohoku Place, Hilo, HI 96720, USA4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

E-mail contact: hwyen at asiaa.sinica.edu.tw

We performed SMA observations in the C18O (2–1) emission line toward six Class 0 and I protostars, to study rotationalmotions of their surrounding envelopes and circumstellar material on 100 to 1000 AU scales. C18O (2–1) emission with

50


http://arXiv.org/pdf/1303.1033

intensity peaks located at the protostellar positions is detected toward all the six sources. The rotational velocities ofthe protostellar envelopes as a function of radius were measured from the Position–Velocity diagrams perpendicular tothe outflow directions passing through the protostellar positions. Two Class 0 sources, B335 and NGC 1333 IRAS 4B,show no detectable rotational motion, while L1527 IRS (Class 0/I) and L1448-mm (Class 0) exhibit rotational motionswith radial profiles of Vrot ∝ r−1.0±0.2 and ∝ r−1.0±0.1, respectively. The other Class I sources, TMC-1A and L1489IRS, exhibit the fastest rotational motions among the sample, and their rotational motions have flatter radial profilesof Vrot ∝ r−0.6±0.1 and ∝ r−0.5±0.1, respectively. The rotational motions with the radial dependence of ∼ r−1 canbe interpreted as rotation with a conserved angular momentum in a dynamically infalling envelope, while those withthe radial dependence of ∼ r−0.5 can be interpreted as Keplerian rotation. These observational results demonstratecategorization of rotational motions from infalling envelopes to Keplerian-disk formation. Models of the inside-outcollapse where the angular momentum is conserved are discussed and compared with our observational results.

Accepted by ApJ


Abstracts of recently accepted major reviews

Observation of rotation in star forming regions: clouds, cores, disks, and jets

Arnaud Belloche1

1 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany

E-mail contact: belloche at mpifr-bonn.mpg.de

Angular momentum plays a crucial role in the formation of stars and planets. It has long been noticed that parcels ofgas in molecular clouds need to reduce their specific angular momentum by 6 to 7 orders of magnitude to participatein the building of a typical star like the Sun. Several physical processes on different scales and at different stages ofevolution can contribute to this loss of angular momentum. In order to set constraints on these processes and betterunderstand this transfer of angular momentum, a detailed observational census and characterization of rotation atall stages of evolution and over all scales of star forming regions is necessary. This review presents the main resultsobtained in low-mass star forming regions over the past four decades in this field of research. It addresses the searchand characterization of rotation in molecular clouds, prestellar and protostellar cores, circumstellar disks, and jets.Perspectives offered by ALMA are briefly discussed.

Accepted by the Proceedings of the Evry Schatzman School 2012 of PNPS and CNRS/INSU on the ”Role andmechanisms of angular momentum transport during the formation and early evolution of stars” (eds. P. Hennebelleand C. Charbonnel)


Formation of the First Stars

Volker Bromm1

1 Department of Astronomy, University of Texas, 2511 Speedway, Austin, TX 78712, USA

E-mail contact: vbromm at astro.as.utexas.edu

Understanding the formation of the first stars is one of the frontier topics in modern astrophysics and cosmology.Their emergence signaled the end of the cosmic dark ages, a few hundred million years after the Big Bang, leadingto a fundamental transformation of the early Universe through the production of ionizing photons and the initial

51



enrichment with heavy chemical elements. We here review the state of our knowledge, separating the well understoodelements of our emerging picture from those where more work is required. Primordial star formation is unique inthat its initial conditions can be directly inferred from the Lambda Cold Dark Matter (LCDM) model of cosmologicalstructure formation. Combined with gas cooling that is mediated via molecular hydrogen, one can robustly identifythe regions of primordial star formation, the so-called minihalos, having total masses of ∼ 106 M⊙ and collapsing atredshifts z ∼ 20 − 30. Within this framework, a number of studies have defined a preliminary standard model, withthe main result that the first stars were predominantly massive. This model has recently been modified to include aubiquitous mode of fragmentation in the protostellar disks, such that the typical outcome of primordial star formationmay be the formation of a binary or small multiple stellar system. We will also discuss extensions to this standardpicture due to the presence of dynamically significant magnetic fields, of heating from self-annihalating WIMP darkmatter, or cosmic rays. We conclude by discussing possible strategies to empirically test our theoretical models.

Accepted by Rep. Prog. Phys.


MRI-driven angular momentum transport in protoplanetary disks

Sebastien Fromang1

1 Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/Service d’Astrophysique, CEASaclay F-91191Gif-sur-Yvette, France

E-mail contact: sebastien.fromang at cea.fr

Angular momentum transport in accretion disk has been the focus of intense research in theoretical astrophysics formany decades. In the past twenty years, MHD turbulence driven by the magnetorotational instability has emergedas an efficient mechanism to achieve that goal. Yet, many questions and uncertainties remain, among which thesaturation level of the turbulence. The consequences of the magnetorotational instability for planet formation modelsare still being investigated. This lecture, given in September 2012 at the school ’Role and mechanisms of angularmomentum transport in the formation and early evolution of stars’ in Aussois (France), aims at introducing thehistorical developments, current status and outstanding questions related to the magnetorotational instability thatare currently at the forefront of academic research.

Accepted by proceedings of the Evry Schatzman School 2012 on the ”Role and mechanisms of angular momentumtransport during the formation and evolution of stars” (eds. P. Hennebelle and C. Charbonnel)


Cosmic-ray propagation in molecular clouds

Marco Padovani1 and Daniele Galli2

1 Laboratoire de Radioastronomie Millimetrique, UMR 8112 du CNRS, Ecole Normale Superieure et Observatoire deParis, 24 rue Lhomond, 75231 Paris cedex 05, France2 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

E-mail contact: Marco.Padovani at lra.ens.fr

Cosmic rays constitute the main ionising and heating agent in dense, starless, molecular cloud cores. We reexaminethe physical quantities necessary to determine the cosmic-ray ionisation rate (especially the cosmic ray spectrum atE < 1 GeV and the ionisation cross sections), and calculate the ionisation rate as a function of the column densityof molecular hydrogen. Available data support the existence of a low-energy component (below about 100 MeV)of cosmic-ray electrons or protons responsible for the ionisation of diffuse and dense clouds. We also compute theattenuation of the cosmic-ray flux rate in a cloud core taking into account magnetic focusing and magnetic mirroring,following the propagation of cosmic rays along flux tubes enclosing different amount of mass and mass-to-flux ratios.We find that mirroring always dominates over focusing, implying a reduction of the cosmic-ray ionisation rate by afactor of 3-4 depending on the position inside the core and the magnetisation of the core.

Accepted by ”Cosmic Rays in Star-Forming Environments”, Proceedings of the 2nd Session of the Sant Cugat Forumon Astrophysics. D. F. Torres and O. Reimer (Editors), 2013, Springer


52




Dissertation Abstracts

Determination of physical conditions in the accretion spots of T Tauristars based on analysis of their spectra

A. V. Dodin

Thesis work conducted at: Sternberg Astronomical Institute, Moscow State University, Russia

Current address: Sternberg Astronomical Institute, Moscow 119991, Universitetskii pr. 13, Russia

Electronic mail: dodin [email protected]

Ph.D dissertation directed by: Sergei Lamzin

Ph.D degree awarded: May 2013

We have calculated the structure and emergent spectrum of a hot spot that appear on CTTS surface due to heatingby radiation from an accretion shock. For the first time not only continuum but also line emission of the hot spot wastaken into account. Our calculations confirmed hypotheis of Petrov et al. (2001), Gahm et al. (2008) and Petrov et al.(2011) that the strongest of these lines manifest themselves as narrow components of helium and metal emission lines,while the weaker ones decrease significantly the depth of photospheric absorption lines, although until now, this effecthas been thought to be due to the emission continuum alone. It appeared that the relative contribution of lines to theveiling increased with decreasing accretion flux, i.e. veiling by lines is the most important for CTTSs with moderateveiled spectra. We found that neglecting the contribution of lines to the veiling could produce an appreciable errorsin determining the effective temperature, interstellar extinction, radial velocity, and v sin i for CTTS.

Assuming the pre-shock gas density N0 and velocity V0 to be the same at all points of the accretion stream cross section,we have calculated the spectrum of the star+circular spot system at various N0, V0, and parameters characterizing thestar and the spot. Using nine stars as an example, we have shown that the theoretical optical spectra reproduce wellthe observed veiling of photospheric absorption lines in 0.4-1.2 µm spectral band, as well as the profiles and intensitiesof the so-called narrow components of He II and Ca I emission lines with an appropriate choice of parameters. Theaccreted gas density N0 in all of the investigated stars except DK Tau has been found to be > 1012 cm−3.

We have discovered a longitudinal magnetic field Bz in the hot accretion spot in three classical T Tauri stars: DOTau, DR Tau and DS Tau. In all three stars the magnetic field is detected at a level above 2σ in the formation regionof the narrow component of the He I 5876 A emission line. In the case of DS Tau the longitudinal field Bz in the hotspot was also measured from the narrow emission components of the Na I D lines, implying +0.8± 0.3 kG, which isequal to the Bz field component measured from the He I 5876 A line.

Eleven new measurements of the magnetic field were obtained in case of fourth star: RW Aur A. We found that Bz inthe formation region of He I 5876 line’s narrow component varied from −1.47± 0.15 kG to +1.10± 0.15 kG. Our dataare consistent with a stellar rotational period of ≃ 5.6d and with a model of two hot spots with an opposite polarity ofthe magnetic field and with a difference in a longitude about 180o. The spot with Bz < 0 is located at the hemisphereabove the midplane of RW Aur’s accretion disc and the spot with Bz > 0 is below the midplane. The following upperlimits for Bz (at 3σ level) were found after averaging of all our observations: 180 G for photosperic lines, 220 G and230 G for formation regions of Hα and [OI] 6300 lines respectively. Upper limit 600 G were found in the region wherebroad components of emisson lines form. For two cases out of 11 we observed the field in a formation region of a blueabsorption wing of Na I D lines i.e. in an outflow: Bz = −180± 50 G and −810± 80 G.

53

Radiative Transfer Models of Protoplanetary Disks: Theory vs.Observations

Gijs Mulders

API, University of Amsterdam

API, Postbus 94249, 1090 GE, Amsterdam, Netherlands

Address as of September 2013: LPL, University of Arizona, 1629 E University Blvd, Tucson AZ 85721

Electronic mail: gdmulders at gmail.com

Ph.D dissertation directed by: Carsten Dominik

Ph.D degree awarded: March 2013

What can we learn about planet formation by observing protoplanetary disks, the planet forming regions aroundyoung stars? To answer such a question, we need to connect the radiative transfer models that we use to interpretthese observations, to theoretical models that describe the physics in these disks.

In this thesis, I have used the radiative transfer code and disk modeling tool MCMax to fit spectral energy distributions,images, spectra and interferometric visibilities of the dust in protoplanetary disks. We combine these with theoreticalmodels of dust settling and grain growth – the first steps of planet formation – and the dynamical impact of giantplanets – a possible end point of planet formation.

We find that, contrary to previous results, the first steps of planet formation are independent of the host star. Wealso zoom in on HD 100546, a transitional disk with a large annular gap. We find the it harbors large dust aggregatesin its surface layers, and that its unusual mineralogy is connected to the presence of the gap. Using hydrodynamicalmodels, we show that the gap is likely caused by a companion brown dwarf, rather than a giant planet.

http://dare.uva.nl/en/record/440375

54

http://dare.uva.nl/en/record/440375

Warm and Cold Gas in Low-Mass ProtostarsHerschel Space Observatory and Ground-Based Surveys

Umut Yıldız

Thesis work conducted at: Leiden Observatory, Leiden University, The Netherlands

Current address: Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

Address as of Sep 2013: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive,Pasadena CA, 91109, USA

Electronic mail: [email protected]

Ph.D dissertation directed by: Ewine F. van Dishoeck and Lars E. Kristensen

Ph.D degree awarded: May 2013

The primary focus of this thesis is the study of physics and chemistry of low-mass young stellar objects (YSOs) usingdata on CO and O2 obtained by the Herschel Space Observatory, complemented by ground-based observations fromAPEX and the JCMT. High-J CO lines (Jup≥5) toward 26 sources in the sample are observed (Eup/kB ∼250-300 K)with the “Heterodyne Instrument for the Far Infrared” (HIFI) onboard Herschel, in order to trace warm material(T≥50 K) in the protostellar envelopes, where previous studies concentrated on low-J CO (Jup≤4) lines, thus tracinglower temperatures.

We found that CO and its isotopologs have different line profiles tracing different material in the protostellar regions(outflows vs. quiescent gas). The excitation conditions for embedded Class 0 and Class I protostars are similar withTkin ∼100–200 K, and does not change with the increasing Lbol, Menv and n(1000 AU). Radiative transfer modelingwas performed to determine the CO abundance structure in the envelope for some of the sources. Analysis of theC18O lines resulted in evidence for significant freeze-out in the coldest regions and evaporation back into the gas phasein the parts of the envelope where the temperature exceeds 25 K. Interestingly, the inner abundance was found to belower than the canonical value of 2.7×10−4, indicating processing of CO into other species. The effect of dust opacityis found very low even in the higher-J C18O transitions. Through our 13CO 6–5 maps, we presented the first directobservational evidence of the location and the quantification for the UV-heated gas around the outflow cavity walls,where its mass is found comparable to the mass of the outflow. This result shows that close to the source position onscales of a few thousand AU, UV heating is just as important as shock heating in terms of exciting CO.

Molecular oxygen, O2 at 487 GHz was observed toward a deeply embedded low-mass Class 0 protostar, NGC 1333-IRAS 4A with the HIFI. The deep spectrum fails to detect O2 at the velocity of the dense protostellar envelope,implying one of the deepest abundance upper limits of O2/H2 at ≤6×10−9 (3σ). Pure gas-phase models and gas-grainchemical models require a long pre-collapse phase (∼0.7–1×106 years) to explain the absence of O2 in the protostellarenvelope. Moreover, a tentative (4.5σ) detection of O2 is seen at the velocity, shifted by 1 km s−1 relative to theprotostar, implying emission originates from the surrounding more extended NGC 1333 molecular cloud.

https://openaccess.leidenuniv.nl/handle/1887/20855

55

https://openaccess.leidenuniv.nl/handle/1887/20855

Meetings of Possible Interest

Massive Stars: From Alpha to Omega

10 - 14 June 2013 Rhodes, Greecehttp://a2omega.astro.noa.gr

Lin-Shu Symposium: Celebrating the 50th Anniversary of the Density-Wave Theory

24 - 28 June 2013 Beijing, Chinahttp://events.asiaa.sinica.edu.tw/conference/20130624/

Physics at the Magnetospheric Boundary

25 - 28 June 2013 Geneva, Switzerlandhttp://www.isdc.unige.ch/magbound/

Protostars and Planets VI

15 - 20 July 2013 Heidelberg, Germanyhttp://www.ppvi.org

Dust Growth in Star & Planet Formation 2013

22 - 25 July 2013 MPIA, Heidelberg, Germanyhttp://www.mpia.de/DG13/

2013 Sagan Summer Workshop: Imaging Planets and Disks

29 July - 2 August 2013 Pasadena, CA, USAhttp://nexsci.caltech.edu/workshop/2013/

IAUS 302 - Magnetic Fields Throughout Stellar Evolution

26 - 30 August 2013 Biarritz, Francehttp://iaus302.sciencesconf.org

Meteoroids 2013. An International Conference on Minor Bodies in the Solar System

26 - 30 August 2013 Dep. of Physics, A.M. University, Poznan, Polandhttp://www.astro.amu.edu.pl/Meteoroids2013/index.php

Exoplanets and Brown Dwarfs

2 - 5 September 2013 de Havilland, University of Hertfordshire, Hatfield, Nr. London, UKno web site yet

Evolution of Star Clusters: From Star Formation to Cosmic Ages

24 - 27 September 2013Splinter Meeting E at the Annual Meeting of the Astronomische Gesellschaft, Tubingen, Germanyhttp://www-astro.physik.tu-berlin.de/~harfst/AG2013_SplinterE/

Dust Radiative Transfer - Codes and Benchmarks 9 - 11 October 2013http://ipag.osug.fr/RT13/index.php

400 Years of Stellar Rotation

17 - 22 November 2013, Natal, Brazilhttp://www.dfte.ufrn.br/400rotation/

The Life Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments

18 - 22 November 2013 Taipei, Taiwanhttp://events.asiaa.sinica.edu.tw/meeting/20131118/

An Olympian Symposium for Star Formation

26 - 30 May 2014 Paralia Katerinis, Mount Olympus, Greecehttp://zuserver2.star.ucl.ac.uk/$\sim$tb/

56

http://a2omega.astro.noa.gr

http://events.asiaa.sinica.edu.tw/conference/20130624/

http://www.isdc.unige.ch/magbound/

http://www.ppvi.org

http://www.mpia.de/DG13/

http://nexsci.caltech.edu/workshop/2013/

http://iaus302.sciencesconf.org

http://www.astro.amu.edu.pl/Meteoroids2013/index.php

http://www-astro.physik.tu-berlin.de/~harfst/AG2013_SplinterE/

http://ipag.osug.fr/RT13/index.php

http://www.dfte.ufrn.br/400rotation/

http://events.asiaa.sinica.edu.tw/meeting/20131118/

http://zuserver2.star.ucl.ac.uk/$\sim $tb/

EPoS2014 The Early Phase of Star Formation

1 - 6 June 2014 Ringberg Castle, Tegernsee, Germanyhttp://www.mpia-hd.mpg.de/homes/stein/EPoS/epos.php

The Dance of Stars: Dense Stellar Systems from Infant to Old

2 - 6 June 2014 Bad Honnef, Germanyhttp://www.astro.uni-bonn.de/$\sim$sambaran/DS2014/index.html

The 18th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun

9 - 13 June 2014 Flagstaff, Arizona, USAhttp://www2.lowell.edu/workshops/coolstars18/

Summer School on Protoplanetary Disks: Theory and Modeling meet Observations

16 - 20 June 2014 Groningen, The Netherlandsno website yet

Living Together: Planets, Stellar Binaries and Stars with Planets

8 - 12 September 2014 Litomysl Castle, Litomysl, Czech Republichttp://astro.physics.muni.cz/kopal2014/

Planet Formation and Evolution 2014

10 - 12 September 2014 Kiel, Germanyhttp://www1.astrophysik.uni-kiel.de/$\sim$2014/main/

Towards Other Earths II. The Star-Planet Connection

15 - 19 September 2014 Portugalhttp://www.astro.up.pt/toe2014

Other meetings: http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

57

http://www.mpia-hd.mpg.de/homes/stein/EPoS/epos.php

http://www.astro.uni-bonn.de/$\sim $sambaran/DS2014/index.html

http://www2.lowell.edu/workshops/coolstars18/

http://astro.physics.muni.cz/kopal2014/

http://www1.astrophysik.uni-kiel.de/$\sim $2014/main/

http://www.astro.up.pt/toe2014

http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

Short Announcements

CORNISH (Co-Ordinated Radio ’N’ Infrared Survey for High-mass starformation): Data release

Here we announce the public release of the on-line database for the CORNISH survey. This is a 5 GHz, 1.5 arcsecondresolution, VLA continuum survey of the portion of the northern Galactic plane that was also covered by the SpitzerGLIMPSE I survey. It was designed to give a complete sample of ultra-compact H II regions as well as providingcomplementary data to the many other surveys that cover the same region of the plane (Hoare et al. 2012). Theon-line database contains the high reliability (7σ) catalogue described by Purcell et al. (2013), which has about 250ultra-compact H II regions amongst the nearly 3000 sources. All sources have been visually inspected for qualitycontrol and object type classification. The database contains individual pages for each source with information andcutouts of complementary data from other IR, millimetre and radio surveys. You can also download an image or theuv data for any location within the survey. If you make use of these data then please cite the original references. Thedatabase can be found at http://cornish.leeds.ac.uk.

Melvin Hoare, on behalf of the CORNISH team

ACS Astrochemistry Subdivision Opens Up Affiliate Status for AAS andDPS MembersThe recently established Astrochemistry Subdivision http://www.chem.hawaii.edu/Bil301/ACSAstrochemistry.htmlof the Division of Physical Chemistry of the American Chemical Society (ACS) http://phys-acs.org invites members ofthe American Astronomical Society (AAS) and of the Division of Planetary Sciences (DPS) to join the ACS Astrochem-istry Subdivision http://www.chem.hawaii.edu/Bil301/ACSAstrochemistryjoin.html as an Affiliate Member. Pleasecomplete a division application form http://portal.acs.org/portal/PublicWebSite/membership/td/join/CTP 004160and email [email protected] or fax (614-4473671) it to ACS Member Services. Note that the PHYS annual membershipdues are US$15, which should be remitted with the form. Please indicate that you would like to join the AstrochemistrySubdivision.

The Subdivision of Astrochemistry provides an interdisciplinary ”home” for individuals interested in astrochemicallyrelated research via experiments, theory, observations, space missions, and modeling. Astrochemistry is the study ofthe abundances and chemical reactions of atoms, molecules, and ions and how they interact with radiation in the gasphase and in the condensed phase in Solar Systems and in the Interstellar Medium (ISM) leading to the formation andbreaking of chemical bonds. Astrochemistry presents both an interdisciplinary and a multidisciplinary field with tiesto the traditional disciplines chemistry, planetary science, chemical biology, physics, and astronomy. Here, chemistry,defined as the change of matter is vital in unraveling the chemical and astrobiological evolution of matter on themicroscopic (elementary chemical reactions) and also on the macroscopic level (planets, moons, interstellar medium).Since the present composition of each macroscopic environment reflects the matter from which it was formed and thechemical processes which have changed the chemical nature since the origin, a detailed investigation of the processesaltering the chemical composition of the pristine environment is critical to rationalize its contemporary makeup and tounderstand its origin and chemistry. Astrochemistry exploits molecular tracers to rationalize the origin and chemicalevolution of the Interstellar Medium and of Solar Systems by combining laboratory studies (chemical dynamics andkinetics, spectroscopy), theoretical chemistry, astrochemical modeling, astronomical observations, and space missions.This work requires a concerted interdisciplinary relationship between chemists, physicists, astronomers, chemicalbiologists, and planetary scientists.

We would also like to thank those of you who supported the establishment of the Astrochemistry Subdivision! Wehope that this creates a thriving Astrochemistry Subdivision that is able to serve the community.

58

http://cornish.leeds.ac.uk

Best regards,

Ralf Kaiser (Chair), Arthur Suits (Chair-Elect), Martin Head-Gordon (Vice-Chair)

Moving ... ??

If you move or your e-mail address changes, pleasesend the editor your new address. If the Newsletterbounces back from an address for three consecutivemonths, the address is deleted from the mailing list.

59

THE STAR FORMATION NEWSLETTER · 2013-06-08 · The Star Formation Newsletter is a vehicle for ......

Documents

Transcript of THE STAR FORMATION NEWSLETTER · 2013-06-08 · The Star Formation Newsletter is a vehicle for ......