Handbook of Star Forming Regions Vol. IIAstronomical Society of the Pacific,c©2008Bo Reipurth, ed.

Star Formation in Bok Globules and Small Clouds

Bo Reipurth

Institute for Astronomy, University of Hawaii640 N. Aohoku Place, Hilo, HI 96720, USA

Abstract. While most star formation occurs in giant molecular clouds, numeroussmall clouds and Bok globules are known to each harbor one or a few young stars.Studies of such isolated newborn stars offer insights into the star formation processunencumbered by the confusion that often complicates studies of richer star formingregions. In this chapter, a dozen Bok globules and small clouds have been selected fordiscussion as examples of small scale star formation. Particularly interesting or wellstudied cases include BHR 71, CG 12, B62, B93, L723, and B335.

1. Introduction

Many Bok globules are known across the sky, and small clouds and cloud fragmentsare found even more commonly. Despite their numbers, these small objects are not animportant contributor to the production of low-mass stars in our Galaxy, accounting forat most a few percent (Reipurth 1983). The importance of these regions lies mostly intheir simplicity, which allows us to study the formation of one or a few stars withoutthe confusion that often complicates observations of richer regions of star formation.

Bok globules are now widely regarded as remnant cloud cores that have been ex-posed due to the presence of nearby OB stars (Reipurth 1983). The specific processesinvolved has been under some debate among theoreticians (e.g., Sandford, Whitaker, &Klein 1984, Bertoldi 1989, Lefloch & Lazareff 1994, Kessel-Deynet & Burkert 2003,Miao et al. 2006). While observational evidence for star formation in Bok globules waslate in coming (e.g., Bok 1978, Reipurth 1983, Yun & Clemens 1990), numerous casesof star formation in globules are now known. Many surveys have been made of glob-ules at various wavelengths, including Clemens & Barvainis (1988), Yun & Clemens(1992), Bourke, Hyland, & Robinson (1995), Bourke et al. (1995), Wang et al. (1995),Launhardt & Henning (1997), Henning & Launhardt (1998), Launhardt et al. (1998),Huard, Sandell, & Weintraub (1999), Moreira et al. (1999), Ogura, Sugitani, & Pickles(2002), and Kandori et al. (2005).

The distinction between a Bok globule and a small cloud is diffuse, as are theterms themselves. The termglobuleoriginated in the papers by Bok & Reilly (1947)and Bok (1948), who already then noted that“It is not a simple matter to draw the linebetween true globules and minor condensations in dark lanes or in regions of variableobscuration.” Bok & Reilly distinguished between small globules, which are seen incontrast against bright HII regions, and large globules; it is these latter that are nowknown as Bok globules. On empirical grounds, Bok considered these objects to be“compact mostly near-circular dark nebulae”with diameters typically between 3 and20 arcmin, corresponding to radii likely in the range 0.15 to 0.8 pc (Bok 1977). Anumber of very interesting star forming clouds exist which are sometimes not much

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larger than Bok globules, and for lack of a better term they are here denoted as“smallclouds”. Some clouds, like L810, which have the shape and angular diameter to fallin the category of Bok globules turn out to have such large distances that they do notqualify as bona fide Bok globules, and they too are considered small clouds.

Many cases of star formation in globules and small clouds are presented through-out this Handbook, for example cometary globules in the Gum Nebula are discussed inthe chapter on Puppis-Vela, B68 and FeSt 1-457 are presented in the chapter by Alveset al., the globules B362 and L1014 are discussed in the chapter on Cygnus, and nu-merous small clouds are reviewed in the chapter on Cepheus. So many cases are knownacross the sky that it would be impossible to discuss all here. The following is thereforea very limited selection rather than an attempt to do a more comprehensive presenta-tion (see Table 1). Inevitably the discussion focuses on globules or small clouds thathave caught the interest of the author, but hopefully the selection is representative ofthe many known cases of star formation in globules and small clouds. The sections areordered after right ascension.

Table 1. Bok Globules and Small Clouds discussed in this Chapter

Object α2000 δ2000 l b Other ID’s

L1438 04:56.9 +51:31 156.2 +5.3L1439 05:00.1 +52:05 156.1 +6.0 CB 26CB 54 07:04.4 –16:23 229.0 –04.6BHR 71 12:01.7 –65:09 297.7 –2.7 Sa 136, TGU 1840CG 12 13:57.6 –39:59 316.5 +21.1 BHR 92, TGU 1970, MBM 112L43 16:34.5 –15:47 1.4 +21.0 TGU 23B62 17:15.9 –20:56 3.1 +10.0 L100B92 18:15.5 –18:11 12.7 –0.6 L323, CB 125, TGU 135B93 18:16.9 –18:04 13.0 –0.8 L327, CB 131L483 18:17.5 –04:40 24.9 +5.4 TGU 259/P1L723 19:17.9 +19:12 53.0 +3.0B335 19:36.9 +07:34 44.9 –6.5 L663, CB 199L810 19:45.4 +27:51 63.6 +1.7 CB 205

2. Individual Bok Globules and Small Clouds

2.1. V347 Aur in L1438

L1438 is the central core in a low-extinction cloud complex encompassing many smallcores, including L1429, L1430, L1431, L1432, L1433, L1435, L1436, L1437, L1438,and L1439 (CB26) in the catalog of Lynds (1962). The cloud complex is known asTGU 1046 in the cloud atlas of Dobashi et al. (2005), where L1438 is listed as the coreTGU 1046 P1. The region is located at the intersection between Auriga, Perseus, andCamelopardalis, see Figure 1 in the chapter by Straizys & Laugalys in Volume I of thisHandbook. L1438 harbors the variable star V347 Aur = HBC 428 = IRAS 04530+5126(α2000 4:56:57.0,δ2000 +51:30:51;l = 156.2◦, b = 5.3◦), first recognized as variableby Morgenroth (1939). A more detailed photographic study of the light variations wasmade by Wenzel (1978), who found that V347 Aur had four maxima that were consis-tent with a period of about a year. V347 Aur is surrounded by a small reflection nebula

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Figure 1. V347 Aur in its small globule L1438. From the Digitized Sky Survey.

known as GM 1-3 (Gyulbudaghian & Magakian 1977), PP 24 (Parsamian & Petrosian1979), or RNO 33 (Cohen 1980), see Figure 1. A low-dispersion spectrum was takenby Cohen, who noted a rich emission line spectrum superposed on a late-type spec-trum. Herbig (priv. comm.) has obtained several high-resolution spectra of V347 Aur,which show very significant spectral variability. Magakian et al. (2008) has discovereda Herbig-Haro object, HH 715, near V347 Aur. The distance to L1438 is unknown, butits proximity to another globule, L1439 (see next section), might suggest that it is atabout the same distance,∼140 pc.

2.2. L1439

About half a degree from L1438 is another small globule, L1439, also known as CB 26(Clemens & Barvainis 1988). As can be seen in Figure 2, the globule is about 5 ar-cminutes across, and has a faint luminous rim and tail that is facing towards the WSW.Launhardt & Henning (1997) suggested a distance of 300 pc, but based on kinematic ar-guments Launhardt & Sargent (2001) proposed that L1439 is part of the Taurus-Aurigacomplex at a distance of about 140 pc.

The IRAS 04559+5200 source is located towards L1439. Stecklum et al. (2004)have obtained near-infrared images of the globule, and find a bipolar reflection nebula,bisected by a high extinction lane, suggesting the presence of an edge-on circumstellardisk. Using near-infrared imaging polarimetry, Stecklum et al. (2004) find that theilluminator is located towards the center of the extinction lane. About 6 arcmin to the

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Figure 2. The globule L1439 = CB 26 as seen on the red Digitized Sky Survey.The field is 15′ × 15′, and north is up and east is left.

Figure 3. The globule CB 54 as seen on the red Digitized Sky Survey. The fieldis 15′ × 15′, and north is up and east is left.

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NNW of the embedded source and along an axis perpendicular to the extinction lane,Stecklum et al. (2004) noted a Herbig-Haro object, HH 494. Henning et al. (2001)used SCUBA to detect a 850µm source towards the IRAS source. More detailed ob-servations were done by Launhardt & Sargent (2001) with the Owens Valley RadioObservatory millimeter-wave array in the continuum at 1.3 and 2.7 mm, revealing anextended structure about 400 AU wide that precisely coincides with the extinction laneseen in the near-infrared. Additional13CO (1-0) data display a Keplerian rotation pat-tern about an axis perpendicular to the disk. The central illuminating source has a totalluminosity of only∼0.5 L⊙ and an energy distribution consistent with a Class I source(Stecklum et al. 2004).

2.3. CB 54

CB 54 is a small globule from the catalog of Clemens & Barvainis (1988) and locateda little below the Galactic plane in Canis Major. It is associated with a bright rim (seeFigure 3) and is listed as LBN 1042 in the catalog of bright nebulae by Lynds (1965).Launhardt & Henning (1997) adopted a distance of 1.5 kpc, but Henning et al. (2001)recognized the probable association of CB 54 with the molecular complex containingthe nebula BBW 4, for which Brand & Blitz (1993) suggest a kinematic distance of1.1 kpc.

Figure 4. The core of the CB 54 globule as seen in the K-band with2MASSwith known objects identified. The cross marks the position of IRAS 07020–1618,and the large dotted circle shows the 850µm source. The dashed box outlines thearea imaged in the mid-infrared, and white circles with plusses indicate the mid-infrared sources detected. The open square marks the VLA centimeter radio contin-uum source, and the open diamond is an 8µm MSX source. From Ciardi & GomezMartın 2007).

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The globule is associated with the embedded object IRAS 07020–1618, a Class Isource that drives a bipolar molecular outflow with well separated lobes oriented NNEto SSW (Yun & Clemens 1994). Wang et al. (1995) obtained a map of CB 54 inthe C18O (2-1) line and found a dense 100 M⊙ core centered on the IRAS source.Analysis of the line profiles suggest moderate evidence for infall motion in the core.In a follow-up study, Zhou et al. (1996) used the BIMA interferometer to do aperturesynthesis observations of CB 54 in the13CO (1-0) and C18O (1-0) lines, but the collapsesignatures were not found, probably because of confusion with the outflow wings.

Yun (1996) obtained near-infrared images of CB 54, and studied two sources sep-arated by about 10′′ and labeled YCI and YCII, the latter is associated with a red re-flection nebula. Additional nebulosity, known as YCI-SW, is located at the center ofthe IRAS uncertainty ellipse. An 850µm map of the globule by Henning et al. (2001)reveal a cool source coincident with the IRAS source, and this is also the location of awater maser detected by Gomez et al. (2006) and studied in more detail by de Gregorio-Monsalvo et al. (2006). A thermal centimeter radio continuum source has been foundin CB 54 five arcseconds southeast of YCI with the VLA (Yun et al. 1996, Moreira etal. 1997).

In a detailed mid-infrared study of CB 54, Ciardi & Gomez Martın (2007) havefound a small cluster of mid-infrared sources that are spatially coincident with the densecore and submillimeter source found towards the IRAS 07020–1618 source and theYCI-SW nebula (see Figure 4). They additionally note that YCII is likely a Class Isource, whereas the nondetection of YCI at mid-infrared wavelengths suggests it is ina more evolved stage or a background object. Altogether, the currently available dataindicate that CB 54 harbors a small cluster of young stars in early evolutionary stages.

2.4. BHR 71

In a survey for southern dark clouds, Sandqvist (1977) cataloged a small cloud, Sa 136,in the southern constellation of Musca just south-west of the Coalsack (it is seen inFigure 1 of the chapter by Nyman in this volume as the darkest little cloud midwaybetween the southern end of the Coalsack and IC 2948; also see Panorama #6 in theintroductory chapter by Mellinger in Volume I). It is located atα2000 12:01:44δ2000

–65:09.1 (l = 297.7◦, b = –2.7◦). Subsequently it was labeled BHR 71 in the catalog ofsouthern Bok globules by Bourke, Hyland, & Robinson (1995), who noted its associ-ation with the embedded source IRAS 11590–6452. The cloud is listed as TGU 1840in the cloud atlas of Dobashi et al. (2005). Because of its apparent association with theCoalsack, a distance of 200 pc has been used in all studies of BHR 71, although themost recent studies of the Coalsack favor a distance closer to 150 pc (see the chapterby Nyman in this volume).

In a major study of BHR 71, Bourke et al. (1997) observed the globule in CO,13CO, and C18O, as well as NH3, and determined a globule mass of about 40 M⊙. TheCO maps revealed a highly collimated molecular outflow, with lobes of 0.3 pc extendingin opposite directions oriented almost north-south. The data are well modeled by abiconical outflow with a semi-opening angle of 15◦ and an angle to the line-of-sightof approximately 80◦-85◦. The driving source of this outflow is IRAS 11590–6452, aClass 0 source with a bolometric luminosity of∼9 L⊙. The blue outflow lobe is flowingthrough a conical cavity seen in both optical (Figure 5) and infrared (Figure 6) images(Bourke et al. 1993, 1997).

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Figure 5. An optical image of the Bok globule BHR 71 obtained atthe VLT. TheFOV is about 7′ × 7′, with north up and east left. Courtesy Joao Alves.

Figure 6. BHR 71 as seen by the Spitzer Space Telescope.Left: Blue is 3.6µm,green is 4.5µm, and red is 8.0µm. Right: The Spitzer image combined with the op-tical image of Figure 5. Courtesy NASA/JPL-Caltech/T. Bourke/c2d Legacy Team.

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Corporon & Reipurth (1997) discovered two groups of Herbig-Haro knots in BHR71 (see Table 2). HH 320 forms two knots seen against the high extinction region inthe center of the globule, whereas HH 321 consists of two knots in the outflow cavityof IRAS 11590–6452. Yun et al. (1997) obtained infrared H2 images and found furtherembedded shocks.

Table 2. Herbig-Haro Objects in the BHR 71 Globule

Object αa

2000δa

2000

HH 320 A 12 01 32.2 –65 08 13HH 320 B 12 01 31.3 –65 08 05HH 321 A 12 01 36.5 –65 09 33HH 321 B 12 01 39.2 –65 10 17

a: from Bourke (2001)

Garay et al. (1998) observed BHR 71 in transitions of SiO, CS, CH3OH, andHCO+, finding that the abundances of methanol and silicon monoxide in the outflowlobes are enhanced, compared to typical dark clouds, by factors of up to∼40 and 350,respectively. This is likely due to shocks in the outflow lobes that cause the evapora-tion of icy grain mantles, releasing large amounts of ice mantle constituents, such asmethanol, into the gas phase.

Groundbased and ISO observations have revealed not one, but two sources inBHR 71 (Bourke 2001). The two sources have a separation of 17′′, correspondingto 3400 AU at a distance of 200 pc. The brighter source, IRS 1, corresponds toIRAS 11590–6452. Both sources drive molecular outflows and have circumstellar ma-terial, but IRS 1 dominates in both respects. IRS 1 drives the major molecular outflowand the HH 321 knots, whereas IRS 2 powers a much weaker outflow as well as theHH 320 knots. In a CO (3-2) map the second, smaller outflow is fully resolved andshown to be bipolar (Parise et al. 2006). Chen et al. (2008) present a 3 mm dust contin-uum map of BHR 71 which shows that IRS 1 is associated with a strong dust continuumsource, whereas only weak emission is detected from IRS 2. Spitzer observations ofBHR 71 show the shocked outflows from both sources, see Figure 6.

2.5. CG 12

The reflection nebula NGC 5367 was discovered by John Herschel in 1834. A smallCO cloud was found at this location by Van Till, Loren, & Davis (1975). A year later,Hawarden & Brand (1976) found that the cloud is an impressive cometary globule,which they named CG 12, with a tail one degree long. It is also known as TGU 1970(Dobashi et al. 2005), MBM 112 (Magnani, Blitz, & Mundy 1985) and BHR 92(Bourke, Hyland, & Robinson 1995). It is a relatively high-latitude cloud, locatedat l = 316.5◦, b = 21.1◦, corresponding toα2000 13:57.6,δ2000 –39:59. Williams etal. (1977) suggested a distance of 630 pc to CG 12, while Maheswar, Manoj, & Bhatt(2004) measured extinction towards stars closer than and beyond the globule, and de-rived a distance of about 550 pc. With a Galactic latitude of 21◦, CG 12 is located about200 pc above the Galactic plane, far from other dark clouds or sites of star formation.

CG 12 has been observed in various millimeter transitions. White (1993) observedthe globule in CO and C18O, and found a well collimated molecular outflow. Furtherdetailed and extensive millimeter observations by Haikala et al. (2006) and Haikala &

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Figure 7. The large cometary globule CG12. From the blue Digitized Sky Survey.

Olberg (2007) showed that the head of CG 12 harbours three dense cores, CG 12N,CG 12S, and CG 12SW, with the molecular outflow coming from CG 12S. This corecontains the strong point source IRAS 13547–3944 and, offset from this source, a mmcontinuum source which is located at the center of the outflow. The northern corecontains another source IRAS 13546–3941. The magnetic field of CG 12 has beenstudied by Marraco & Forte (1978) and Bhatt, Maheswar, & Manoj (2004).

CG 12 contains five B and A stars. The two most massive form the visual bi-nary h4636, discovered by John Herschel1 and surrounded by a bright reflection nebula(see Figure 7). The binary has a separation of 3.7 arcsec, the northernmost h4636Nis a reddened B4 star (V∼10.7) and h4636S is a B7 star (V∼10.3). Their spectra arevery different, the northern showing strong Hα emission, and the southern having noemission lines (Williams et al. 1977). The third B-star is CoD –39◦8583, which has aspectral type of B8, and is also surrounded by a reflection nebula. The two A-stars aresources 6 and 8 of Williams et al. (1977), source 6 is an A4 star and source 8 an A2 staraccording to Maheswar et al. (2004). Source 8 may be associated with the reflectionnebula Bernes 146 (Bernes 1977). This little cluster of stars was first recognized as agroup of Hα emission line stars by Williams et al. (1977).

1It is interesting to note that when discovered in 1834, h4636 probably was the first pre-main sequencebinary ever seen, albeit only recognized as such much later.

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If one extrapolates a standard IMF from the known intermediate-mass stars, a siz-able population of low-mass young stars is expected. In a major study, Getman et al.(2008) used the Chandra X-ray Observatory to image CG 12 with the ACIS detector,detecting 128 X-ray sources, of which about half are likely to be young stars, mostlylightly obscured T Tauri stars but also including several embedded stars. Using a color-magnitude diagram, Getman et al. estimated ages for the unobscured low-mass popula-tion, and found a large age spread, ranging from<1 Myr for several embedded sourcesto ∼20 Myr. The data are sufficiently uncertain that they are consistent with both acontinuous star formation history and with several distinct episodes of star formation.

CG 12 has a 10 pc long tail, providing a well defined axis, which suggests that anoutside event has led to the cometary morphology of the globule, and at the same timeleading to the star formation activity in the globule (Williams et al. 1977). Surprisingly,the head points away from the Galactic plane, suggesting that the energetic event lead-ing to the cometary morphology took place at an even larger height above the Galacticplane. The HI maps of Cleary, Haslam, & Heiles (1979) and Dickey & Lockman (1990)show a complete HI shell with a diameter of approximately 20◦ and centered at aboutl= 315◦, b = 30◦. CG 12 is close to the edge of this shell and nearly points to its center(Maheswar, Manoj, & Bhatt 2004). A far-infrared shell, GIRL G318+32, is also foundhere (Konyves et al. 2007). Getman et al. (2008) note that a single supernova explosioncannot create such a huge cavity, while a superbubble produced by many supernovaerequires a rich stellar cluster not likely to be found at such a height above the plane.Getman et al. (2008) searched for longer-lived B stars ahead of CG 12 and found half adozen which appear to be at the right distance, including HD 120958, a B3V star whichlies precisely on the rather well defined axis of the cometary globule. They speculatethat HD 120958 could be the relic of a massive binary system of which the primaryexploded as a supernova.

CG 12 is a unique small star forming region, that deserves further studies, whichmay help to understand its enigmatic origin.

2.6. L43

L43 is a small filamentary cloud in the constellation Ophiuchus located at aboutα2000

16:34.5,δ2000 –15:47 (l = 1.4◦, b = +21.0◦). In the cloud catalog of Dobashi et al.(2005) it is listed as TGU 23. L43 was first studied by Elmegreen & Elmegreen (1979),who mapped it in12CO and13CO. They found it to be a thin filament with approximatedimensions of 10′ × 70′, although the region with noticeable extinction is only half ofthose dimensions. It is interesting to note that the long axis of L43 is parallel to thestreamers of theρ Ophiuchi cloud complex (Figure 3 of Herbst & Warner 1981 givesa good overview of the region). Due to the relative proximity to the Ophiuchus cloudcomplex, early work assumed a distance of about 160 pc. Subsequently de Geus etal. (1990) performed a CO survey of the dark clouds in Ophiuchus, and argued for anupper limit to the distance of 130 pc, a distance that has been adopted in much recentwork.

Elmegreen & Elmegreen (1979) noted two nebulous stars in L43, which becamelisted as RNO 90 (HBC 649, IRAS 16312–1542) and RNO 91 (HBC 650, IRAS 16316–1540) in the catalog of Cohen (1980). RNO 90 is irregularly variable, and has the twovariable star designations V1003 Oph = V2132 Oph. The two stars were subsequentlystudied by Herbst & Warner (1981), who obtained optical and infrared photometry ofboth stars, and a spectrum of RNO 90, revealing it to be a rich emission line T Tauri

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star. Optical spectra of both stars were presented by Levreault (1988). Early far-infraredobservations of L43 were obtained by Nordh et al. (1981). A VLA 3.6 cm map of L43detected four sources, one of which coincides with RNO 91.

Figure 8. The small dark cloud L43 with its two nebulous stars,RNO 90 andRNO 91. The latter drives a major bipolar outflow, with the blue lobe to the south-east, and the red lobe to the northwest. North is up and east is left. From Bence etal. (1998).

The reason that L43 has attracted considerable attention goes back to the firstmajor study of the cloud by Mathieu et al. (1988), who discovered a bipolar molecularoutflow emanating from RNO 91. CCD images reveal a clear cavity in the cloud withRNO 91 at its apex and with the blue lobe of the outflow fitting between the cavitywalls. Their NH3 map shows two dense condensations on either side of RNO 91. Themore massive is the one to the east of RNO 91, further mapped in NH3 by Benson& Myers (1989). It has subsequently been detected at 450 and 850µm by Bence etal. (1998), Shirley et al. (2000), Young et al. (2006) and Wu et al. (2007), and hasbeen dubbed L43-SMM. Its magnetic field has been studied by Ward-Thompson et al.(2000) and Crutcher et al. (2004). The RNO 91 outflow was also mapped by Levreault(1988), Myers et al. (1988), and Parker et al. (1988). In a higher resolution CO J =2-1 map, Bence et al. (1998) show that the outflow is slow and poorly collimated, andemerging perpendicularly to the long axis of the L43 cloud (see Figure 8). There is noevidence for a Herbig-Haro jet in the RNO 91 cavity, and Bence et al. (1998) arguethat the best-fitting outflow model is one of a slowly expanding shell. Very detailed

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observations of the molecular outflow in CO were obtained at the BIMA 10 antennainterferometer by Lee et al. (2002), which show the cavity in fine detail. These data,augmented with several more transitions, have been analysed by Lee & Ho (2005),who propose a simple kinematic model with a wide-opening base and an expandingcylindrical shell, representing the late stages in the destruction of the cloud core. Whileno HH objects are known to be associated with RNO 91, there is evidence for shockedmolecular hydrogen (Kumar et al. 1999).

Based on millimeter continuum data, Terebey et al. (1993) suggested that L43 issurrounded by a circumstellar disk, and Andre & Montmerle (1994) present disk modelsfor both RNO 90 and 91. In a detailed study, Weintraub et al. (1994) present infraredspectroscopy of the disk around RNO 91, and find spectral features of frozen H2O,CO, and possibly XCN. Further infrared spectra of water ice in RNO 91 are presentedby Brooke et al. (1999), and a number of ice features are identified by Boogert et al.(2008) using Spitzer data.

The reflection nebula around RNO 91 has been studied by Schild et al. (1989) andScarrott et al. (1993), both of which demonstrate that all of the nebulosity is reflectedlight from RNO 91, a result further supported by the infrared polarimetry of Weintraubet al. (1994). Structure in the infrared nebula is visible in the K-band images of Heyeret al. (1999) and Connelley et al. (2007).

2.7. B62

B62 (= L100) is a well defined globule in Ophiuchus that forms part of the disturbedcloud region east ofρ Ophiuchi and north of B59. It is located atα2000 17:15.9δ2000

–20:56 (l = 3.1◦, b = +10.0◦). Since the globule was discovered by Barnard (1919)(see Figure 5 in the chapter by Alves, Lombardi, & Lada in this volume) it was paidno attention until Cohen (1980) noted the presence of two faint nebulous stars, RNO92 and 93, towards the globule. In a subsequent study, Reipurth & Gee (1986) foundfour Hα emission stars, including RNO 92/93, and most recently Reipurth et al. (2008)found a fifth faint Hα emission star in the globule. Coordinates for these 5 stars aregiven in Table 3. Whereas B62-Hα 1, 2, 3, and 5 are projected towards the denseglobule and are associated with reflection nebulae, B62-Hα4 is located well above theglobule towards the northeast. Plaut (1968) noticed the variability of B62-Hα3, leadingto its inclusion in the GCVS as V1725 Oph. B62-Hα1 was found by Reipurth & Gee(1986) to be a visual binary with a separation of 4.4 arcsec. It was observed in thenear-infrared by Chelli et al. (1995), who found the companion to dominate the systemat L-band.

Table 3. Hα emission stars in the B62 globule

Star α2000 δ2000 SpTa Other ID’s

B62-Hα1 17 15 55.7 –20 56 03 M0 RNO 92, HBC 658B62-Hα2 17 16 11.7 –20 57 55 M2 HBC 659B62-Hα3 17 16 13.8 –20 57 46 M0.5 RNO 93, HBC 661, V1725 OphB62-Hα4 17 16 13.1 –20 54 29 M3 HBC 660B62-Hα5 17 16 11.0 –20 57 38a: from Reipurth & Gee (1986)

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The embedded source IRAS 17130–2053 is located towards the center of the glob-ule (Reipurth & Gee 1986), see Figure 10, and is associated with an ammonia core(Anglada et al. 1997). A molecular outflow centered on this source was detected byParker et al. (1988). In a subsequent study, Reipurth et al. (2008) have found thissource to be driving a bipolar Herbig-Haro flow, HH 1000, with a series of bow shocks,visible in the deep Hα image in Figure 9. The image shows that B62 has a flattenedappearance with HH 1000 breaking out perpendicularly to the major axis of the glob-ule through a cone-shaped cavity. Another bipolar HH flow, HH 1001, lies along anENE-WSW axis and is centered on B62-Hα1.

To the south, the diffuse outskirts of B62 is illuminated by the bright late A-starBD –20◦4896. The reflection nebula is known as vdB 110 (van den Bergh 1966).

Figure 9. The Bok globule B62. The five Hα emission stars B62-Hα1-5 are la-beled. The embedded source in the middle of the globule, IRAS 17130–2053, ispowering a bipolar Herbig-Haro flow, HH 1000, perpendicular to the main axis ofthe globule. The young binary B62-Hα1 drives another bipolar Herbig-Haro flow,HH 1001, towards ENE and WSW. The bright star BD−20◦4896, an interloper, isilluminating the globule from beneath the edge of the image. The field of view isabout 7′ × 9′, and north is up and east is left. Image obtained through an Hα filter atthe 8m Subaru telescope. From Reipurth et al., in preparation.

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Figure 10. The B62 globule seen in a JHK color mosaic from 2MASSdata. Thefield is the same as in Figure 9. The IRAS 17130–2053 source that drives theHH 1000 outflow is seen at the center of the globule. Courtesy Colin Aspin.

There is no evidence that the star is young, and it may well be just accidentally passingthrough the tenuous envelope of the globule. Using Stromgren photometry of the starand assuming that the star is of luminosity class V, Reipurth & Gee (1986) estimated adistance to BD–20◦4896, and thus to B62, of 225±25 pc.

Just north of B62 is the cometary globule B61 (L111), which is smaller but alsohighly opaque (Reipurth & Gee 1986). The bright rim is facing towards the only O-starin the vicinity, the O9.5 V runaway starζ Oph that is moving away from the Sco-Cenassociation (see the chapter by Preibisch and Mamajek in this volume).

2.8. B92 and B93

Barnard (1913) drew attention to two small markings within the rich star clouds ofSagittarius. They later received the identifications B92 and B93 in his catalog of darkclouds (Barnard 1919). These objects were among those that Barnard singled out in hisarguments that the dark clouds were real objects, and not just voids of stars. Figure 11shows the two objects as seen on the Digitized Sky Survey, B92 (aka L323, TGU 135,CB 125) is the larger (approximately 15′

× 9′) cloud to the west, and B93 is the smallercometary cloud to the east. The two clouds are located just north of the large L291cloud and are projected against the rich patch of the Milky Way known as M24, orpopularly as the “Sagittarius Star Cloud” (see also Figure 1 of the chapter by Reipurth,Rodney, & Heathcote in this volume). The cloud coordinates for B92 areα2000 18:15.5,δ2000 –18:11 (l = 12.7◦, b = –0.6) and for B93 they areα2000 18:16.9, δ2000 –18:04(l = 13.0◦, b = –0.8).

There is some confusion in the literature about the Lynds designation of B93.SIMBAD lists it as L327, but many authors refer to it as L328. When plotting thecoordinates on the DSS, L328 corresponds to the dense head of the globule, and L327to the tenuous tail. The preferred nomenclature should be B93, but when a Lyndsnumber is used, preference should be given to L328.

15

Figure 11. The two Bok globules B92 and B93. B92 is the larger cloud (about9′×15′) to the west, and B93 is the smaller cometary cloud to the east. From theDigitized Sky Survey. North is up and east is left. Coordinates are for J2000.

Figure 12. The Bok globule B92 as seen on a red ESO Schmidt platefrom theDigitized Sky Survey. The young star B92-IRS is indicated. The field is 15′

× 15′.

16

Bok & McCarthy (1974) adopted a distance of 200 pc for B92, because of theabsence of many foreground stars to the globule and because of its relative proximityto the Ophiuchus clouds. This distance has been used in many later studies, but isobviously little more than an educated guess. Stellar luminosities derived on the basisof this distance should be viewed with considerable caution.

Various surveys have been made in search of young stars in B92 and B93. Ogura& Hidayat (1985) searched both globules for Hα emission stars, but did not find any.Clemens & Barvainis (1988) listed a number of IRAS sources found in the generaldirection of B92 (their object CB 125), but none are likely to be related to the globule.

A map of B92 in C18O and NH3 by Lemme et al. (1996) show several cores.Deep CCD-images of B92 have revealed a faint nebulous star near the center of B92and located at the edge of an elongated cavity through which background stars canbe seen (Reipurth, unpublished). This object, B92-IRS, is marked in Figure 12, it ispresumably a young star that through outflow activity has blown the cavity seen in theglobule. The star is located atα2000 18:15:36.1,δ2000 –18:12:11.

Figure 13. The Bok globule B93 = L328 contains a small cluster of cold dustcores as seen in this 350µm SHARC-II map obtained by Wu et al. (2007). The coreL328-SMM2 may contain a very low luminosity protostar.

B93 has been observed at 450 and 850µm with SCUBA on JCMT by Visser etal. (2001, 2002), who found a cold core in the center of the dense head of B93. Their5-point map in12CO J=2-1 did not reveal any outflow. Wu et al. (2007) observed theglobule at 350µm and found three cold condensations (see Figure 13), of which Spitzerobservations indicate that SMM2 may possibly contain a very low-luminosity protostar.

2.9. L483

The small L483 cloud is located towards the Aquila Rift at Galactic coordinatesl =24.9◦, b = +5.4◦, and it is widely assumed that it is associated with the Rift at a distanceof ∼200 pc (Dame & Thaddeus 1985). It forms a dense core in a small cloud that islabeled TGU 259 in the cloud atlas of Dobashi et al. (2005), and that also encompassesthe Lynds clouds 475, 476, 477, 479, and 482 (Figure 14).

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Figure 14. The small cloud L483 is located in the Aquila Rift. The figure showsan excerpt from the extinction atlas by Dobashi et al. (2005), the abscissa is Galacticlongitude from 21◦ to 30◦ and the ordinate is Galactic latitude from +1◦ to +10◦.

L483 contains the source IRAS 18148–0440, which was first identified as an em-bedded young object by Parker (1988), and its very red colors compared to many otherembedded sources were subsequently recognized (Parker 1991, Ladd et al. 1991a). Aprominent molecular outflow was discovered by Parker et al. (1991). A thermal radiocontinuum source has been detected towards IRAS 18148–0440 atα2000 18:17:29.87δ2000 –4:39:38.8 (Beltran et al. 2001). The source has a luminosity of about 10 L⊙

(Fuller et al. 1995), and its energy distribution indicates that it is a Class 0 source(Fuller et al. 1995, Fuller & Wootten 2000) although it appears to be in transition to-wards a Class I source (Tafalla et al. 2000, Pezzuto et al. 2002). The source is locatedin a dense core detected in ammonia by Fuller & Myers (1993) and Anglada et al.(1997), and mapped at higher resolution with the VLA by Fuller & Wootten (2000).The core has been mapped in other transitions by Tafalla et al. (2000). Maps of thecircumstellar envelope in the submillimeter lines of CS (J = 7-6) and HCN (J = 4-3)obtained at the ASTE telescope are presented by Takakuwa et al. (2007), which showthat warm gas (>40 K) is present as much as 4000 AU from the source. Using theBIMA interferometer, Park et al. (2000) mapped the distribution of C3H2 212–101 andfound an extended envelope with a size of∼3000× 2000 AU. Jørgensen (2004) pre-sented a millimeter-wavelength aperture synthesis study of the envelope in 8 molecularspecies using the OVRO Millimeter Array and found evidence for chemical differenti-ation around the source. Dense material close to the central protostar shows a velocitygradient perpendicular to the outflow axis, consistent with rotation around a∼1 M⊙

central object.

18

Figure 15. The source IRAS 18148–0440 is embedded in the smallcloud L483and drives a finely collimated molecular outflow, see here in an integrated intensitymap of12CO 4-3. The upper panel shows redshifted emission, and the lower panelblueshifted emission. The VLA position of the source is marked by a star. Crossesand circles mark positions where12CO 2-1 and13CO 2-1 spectra were taken, re-spectively. Strong H2 emission is found at the location of the square with an arrow.From Hatchell et al. (1999).

Early far-infrared and submillimeter maps of the L483 source were presented byLadd et al. (1991b), who found the emission to be extended. The source has sub-sequently been mapped repeatedly with SCUBA at 450 and 850µm (e.g. Fuller &Wootten 2000, Shirley et al. 2000, Visser et al. 2002). The dust continuum emissionis extended, principally in the northeast to southwest direction. Shirley et al. (2002)used a one-dimensional radiative transfer code to model these maps, and found that thedust continuum emission is best fitted by a shallow (p = 1.2) power law. The internalluminosity of the model is 13 L⊙, making the contribution from the interstellar radia-tion field negligible in comparison. Jørgensen et al. (2002) also used a one-dimensionalradiative transfer code to model the envelope of the L483 source, and also found a bestfit with a shallow power law. Jørgensen (2004) obtained continuum emission maps at2.7-3.4 mm with the OVRO Millimeter Array, and found the data to be well fitted byan extended envelope model without introducing a disk or compact source.

Indications of gravitational infall in IRAS 18148–0440 was noted in high resolu-tion line studies by Myers et al. (1995), Mardones et al. (1997), Park et al. (1999),Fuller & Wootten (2000), and Tafalla et al. (2000).

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Figure 16. The bipolar reflection nebula around IRAS 18148–0440 in L483 isseen in this K-band image. The source is located in the highly obscured regionbetween the two lobes. The field is approximately 50′′

× 70′′, with north up and eastleft. From Connelley et al. (2008).

The molecular outflow discovered by Parker et al. (1991) extends along an east-west line. It was further mapped in CO J = 3-2 by Fuller et al. (1995), in CO J =2-1 by Bontemps et al. (1996), and in CO J = 4-3 by Hatchell et al. (1999), seeFigure 15. Additional multiple transitions were mapped by Tafalla et al. (2000). BIMAinterferometric observations of HCO+ 1-0 by Park et al. (2000) show that the outflowis clumpy, and the opening angle is widest for the slowest moving material. The multi-transition study by Jørgensen (2004) using the OVRO Millimeter Array suggests a clearinteraction between the outflowing gas and the quiescent core. The innermost region ofthe outflow was mapped with the SMA in CO J = 2-1 and other transitions (Jørgensen etal. 2007). Carolan et al. (2008) modeled line profiles of four CO isotopomers towardsthe L483 source in an attempt to probe the distinct physical conditions in the differentcomponents, core, envelope, and outflow.

A bipolar reflection nebula is seen on K-band images, along the same axis as themolecular outflow (Hodapp 1994, Fuller et al. 1995, Connelley et al. 2007). Thewestern part is more prominent (Figure 16) and coincides with the blue outflow lobe.The reflection nebula is highly variable and has been monitored by Connelley et al.(2008). A bipolar molecular hydrogen jet, with the principal lobe aligned with thebrightest lobe of the reflection nebula, was discovered by Fuller et al. (1995) and furtherimaged by Connelley et al. (2008). The jet bow shock was studied with long slitspectroscopy of the infrared H2 lines by Buckle et al. (1999), who suggested that it is aC-shock with shock velocity of 40-45 km sec−1.

An H2O maser is found in association with the embedded source (Wilking et al.1994, Xiang & Turner 1995, Claussen et al. 1996, and Furuya et al. 2003).

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2.10. L723

L723 is a small, rather isolated cloud in the constellation Sagitta, just north of Aquila,located atα2000 19:17.9,δ2000 +19:12.3 (l = 53.0◦, b = +3.0◦). Attention was firstdrawn to this region when Frerking & Langer (1982) carried out a12CO survey of 180Lynds clouds of opacity classes 5 and 6 in search of high velocity line wings; L723 wasone of four regions identified. Goldsmith et al. (1984) plotted reddening vs distancetowards and around the L723 cloud and derived a distance of 300±150 pc, which hasbeen adopted in subsequent studies.

Based on a12CO J=1-0 map towards L723, Goldsmith et al. (1984) found a molec-ular outflow with well separated lobes and evidence that two separate outflows arepresent, a major one oriented east-west, and a smaller one directed north-south. Subse-quent maps in several millimeter transitions with increasing resolution led to a debatewhether there are two almost orthogonal outflows, or a single one with either a wideopening angle or a precessing outflow axis (Moriarty-Schieven & Snell 1989, Avery etal. 1990, Hayashi et al. 1991, Hirano et al. 1998). In a high resolution CO study madewith the BIMA interferometer, Lee et al. (2002) obtained a very detailed outflow map(see Figure 17, which strongly supports the two-flow scenario.

Vrba et al. (1986) discovered two Herbig-Haro knots, which are now known asHH 223. Both are associated with the blueshifted lobe of the main east-west outflow. Amore detailed Hα and [SII] imaging study was made by Lopez et al. (2006), who foundfurther knots of HH 223 along the axis of the principal outflow, see Figure 18. (Notethat Hirano et al. 1998 erroneously refer to some of the knots of Vrba et al. (1986) asHH 82 and 84). Further knots are seen in the infrared (Hodapp 1994, Palacios & Eiroa1999).

The embedded source IRAS 19156+1906 is located at the center of the two out-flows (Davidson 1987). It is a Class 0 source with a luminosity of about 3 L⊙ at theassumed distance of 300 pc. Anglada et al. (1991) used the VLA at 3.6 cm to discovertwo radio continuum sources at the center of the outflows, with a separation of 15′′.In a higher resolution follow-up study, Anglada et al. (1996) noted major differencesbetween the two sources. While VLA 1 is unresolved at the 0.3′′ resolution employed,VLA 2 shows a fine bipolar thermal jet along the axis of the principal molecular out-flow, clearly supporting the identification of VLA 2 as the driving source. Dartois et al.(2005) used the IRS low resolution spectrometer onboard Spitzer to find a very largeCO2 ice column density toward the embedded source.

It is not clear that VLA 1 is driving the smaller N-S oriented flow, becausea) thesource is not detected in the 1.3 mm dust continuum in contrast to VLA 2 (Cabrit &Andre 1991, Reipurth et al. 1993);b) VLA 1 is located outside the dense ammonia gassurrounding VLA 2 detected by Girart et al. (1997); andc) the spectral index of VLA 1is suggestive of a non-thermal source (Anglada et al. 1996). It appears that anothersource is required to drive the smaller N-S outflow.

Indirect evidence for possibly another source in the region was found in the formof an H2O maser discovered by Girart et al. (1997) and further observed by Furuya etal. (2003). Firm evidence has come with a detailed, high resolution radio continuumstudy by Carrasco-Gonzalez et al. (2008), who found a small cluster of sources at thelocation of IRAS 19156+1906. First, they discovered that VLA 2 is a close binarywith a separation of 0.3′′ between the components 2A and 2B. Second, they found thata separate source, 2C, is associated with the H2O maser. Finally they found that yetanother source a few arcseconds to the ESE is associated with a new millimeter con-

21

Figure 17. The region around L723 VLA2 in CO J = 1-0 emission superposedon an H2 image. The beam size is 8′′

× 8′′. The dotted line outlines the observedregion. From Lee et al. (2002).

Figure 18. An Hα CCD image of the center of the L723 cloud with the HH 223flow extended ESE to WNW. The two sources VLA 1 and VLA 2 are marked, as areseveral stars or knots (marked with V) noted by Vrba et al. (1986). From Lopez etal. (2006).

22

tinuum source. Altogether, it appears that VLA 2 constitutes a small newborn multiplesystem, from which the two large molecular outflows emanate.

2.11. B335

The Bok globule Barnard 335 (also known as L663 or CB 199) is located in Aquila (seethe chapter by Prato, Rice, & Dame in Volume I) atα2000 19:36:55,δ2000 +07:34.4 (l =44.9◦, b = –6.5◦). It is a prototypical Bok globule, a tiny dark cloud with a completelyopaque core approximately 2× 3 arcmin along E-W and N-S directions (Figure 19).Bok & McCarthy (1974) estimated an upper limit to its distance of 400 pc from thelack of foreground stars towards the core. Tomita et al. (1979) suggested a distanceof 250 pc derived from star counts, a value supported by Frerking et al. (1987), whosuggests a connection with the Lindblad ring. All later studies have adopted a distanceof 250 pc. At this distance the globule has a diameter of about 0.2 pc. Harvey et al.(2001) noted that they would get a better fit to their color excess data if the globulehad a smaller distance. In a re-examination of the available photometry of stars in thedirection of the globule, Stutz et al. (2008) argue that a distance of 150 pc, with anuncertainty of nearly a factor two, is more appropriate.

B335 has attracted much attention following the discovery of an embedded far-infrared source. Initially the far-infrared flux was ascribed to re-emission of the inter-stellar radiation field (Keene at al. 1980) until the compact nature of the emission wasrecognized (Keene et al. 1983). After the launch of the IRAS satellite this source be-came known as IRAS 19345+0727. The source has low luminosity, L≈ 3 (D/250)2 L⊙

(e.g., Shirley et al. 2000), and no near-infrared counterpart has been detected (Hodapp1998). Stutz et al. (2008) combined Spitzer IRAC and MIPS photometry of the sourcewith existing longer-wavelength data and agree with the abovementioned luminosityestimate, but note that the luminosity is 1.2 L⊙ at their preferred distance of 150 pc.Gee et al. (1985) detected the source at sub-millimeter wavelengths, and argued thatthe object could be a protostar. Andre et al. (1993) classified the source as a Class 0object. Further submillimeter continuum observations were presented by Chandler etal. (1990), who resolved the continuum source in the N-S direction in a 8′′ beam, butnot along an E-W line. The source was detected in the 3.6 cm radio continuum byAnglada et al. (1992, 1998). Further 3.6 cm flux measurements indicate that the sourceshows considerable variability (Avila, Rodrıguez, & Curiel 2001, Reipurth et al. 2002).Far-infrared spectroscopy of the source is reported by Nisini et al. (1999).

IRAS 19345+0727 drives a bipolar molecular outflow oriented east-west, and firstdetected and studied by Frerking & Langer (1982) and Goldsmith et al. (1984). Theflow is well collimated, with a total length-to-width ratio of∼ 5. It moves very close tothe plane of the sky, with an inclination of only 5-10 degrees, such that the blue-shiftedand red-shifted lobes are well separated. The eastern lobe is 0.9 pc long and tiltedtowards us, while the western lobe is 0.4 pc long and tilted away from us (Cabrit et al.1988, Hirano et al. 1988,1992, Moriarty-Schieven & Snell 1989, Stutz et al. 2008).Aperture synthesis maps of13CO, C18O J = 1-0, and 2.7 mm continuum emission showhigh-velocity emission perpendicular to a dense core that is elongated north-south butunresolved along the outflow axis (Chandler & Sargent 1993).

Vrba et al. (1986) and Reipurth, Heathcote, & Vrba (1992) discovered a chainof three little HH objects, HH 119, located on an east-west line and comprising atightly collimated string of optical emission knots emanating from the embedded driv-ing source. HH 119A,B is in the western red lobe of the associated molecular outflow

23

Figure 19. B335 as seen in a color composite based on Hα (red), [SII] (green,and R band (blue) images. Components of the bipolar Herbig-Haro flow HH 119 arelabeled, and several have proper motion vectors indicated. The vector for knot F isdisplaced to fit inside the figure. Red contours show a bipolar reflection nebula asimaged at 8µm with Spitzer, and yellow contours show the location of the sourceat 24µm. The field of view is about 5× 4 arcmin, and North is up and east is left.From Gaalfalk & Olofsson (2007).

and HH 119C in the eastern blue lobe, and proper motions are in opposite directionsaway from the source (Reipurth, Heathcote, & Vrba 1992). Gaalfalk & Olofsson (2007)confirmed and improved these proper motions and discovered further optical and in-frared components of the HH 119 bipolar flow. ISO-LWS spectra were obtained of themain HH 119 knots by Nisini et al. (1999). An H2O maser has been studied by, e.g.,Claussen et al. (1996).

Despite its simple optical morphology, B335 shows considerable structure at mil-limeter wavelengths. It is centrally condensed, with the center of the globule corre-sponding to peaks in the distribution of CS, NH3, C18O, H2CO and HCO+ (e.g., Mar-tin & Barrett 1978, Snell et al. 1982, Menten et al. 1984, Walmsley & Menten 1987,Zhou et al. 1990, Hasegawa et al. 1991, Velusamy, Kuiper, & Langer 1995, Murphy,Little, & Kelly 1998, Saito et al. 1999, Choi 2007, Takakuwa et al. 2007, and Stutzet al. 2008). Zhou et al. (1993) observed five rotational transitions of H2CO and CStoward B335 with high spatial and spectral resolution, and found direct, kinematic ev-

24

idence of collapse motions in the globule as predicted in the inside-out collapse modelof Shu (1977). Zhou (1995) and Choi et al. (1995) calculated theoretical line profiles ofcollapsing cores for comparison with the data for B335. Interferometric observationsof CS J = 5-4 emission by Wilner et al. (2000) do not show dense gas with infall ve-locities approaching 1 km s−1 at 600 AU scales as predicted by the inside-out collapsemodels, but the authors note that additional species and transitions should be observedat similarly high resolution to address possible issues by abundance and/or excitationeffects.

Harvey et al. (2001) used deep HST/NICMOS and Keck near-infrared imagesto probe the structure of B335 using star counts. They find that the radial profile ofthe reddening is well fitted by the inside-out collapse model, but note that an unsta-ble Bonnor-Ebert sphere provides an equally good fit over the radii that the extinctiondata probe. The data show strong evidence for a bipolar conical outflow cavity with asemi-opening angle of 41◦±2◦. In subsequent studies, Harvey et al. (2003a, 2003b)presented subarcsecond-resolution observations from the IRAM PdB Interferometer inthe dust continuum at 1.2 and 3.0 mm. The observations probe the innermost regionson scales of less than 100 AU, and reveal a compact structure around the source thatappears to be a circumstellar disk with radius less than 100 AU. The density structureof the B335 core indicates anr−1.5 inner region in gravitational free fall surrounded byanr−2 envelope.

Frerking et al. (1987) determined the mass of the globule to be 11-14 M⊙, andfound it to be associated with a tail of tenuous gas of dimensions 20′

× 36′, havingan additional mass of about 25 M⊙ and containing several minor condensations. Thismorphology is very reminiscent of the cometary globules studied by Reipurth (1983),and suggests that B335 was once affected by the radiation from a massive star, or possi-bly a supernova. The direction of the tail indicates that such a massive star should havebeen located to the WSW of B335.

Because of its structural simplicity and lack of source confusion, B335 is an ex-cellent target for studying the chemistry of a protostellar region. Evans et al. (2005)have obtained observations of 25 transitions of nine molecules which they compare tomodels of chemical abundances, where the temperatures of dust and gas are calculatedfrom the luminosity of the protostar and the density distribution.

Optical polarization measurements of background stars viewed through the periph-ery of the globule have been reported by Vrba et al. (1986), who find the polarizationvectors to lie along position angle 111◦

±4◦, close, but not equal, to the position angle of

the molecular outflow, which is about 90◦. Hodapp (1987) obtained I-band polarimetryof a larger number of stars, and found a complex distribution of polarization that variesacross B335.

2.12. L810

L810 is a small cloud in Vulpecula located atα2000 19:45:24,δ2000 +27:51.0 (l = 63.6◦,b = 1.7◦). It is also known as CB 205 (Clemens & Barvainis 1988) or Khavtassi 657(Khavtassi 1955). It is a fairly round cloud with a diameter of about 6 arcmin (e.g. Bok1977, Bok & Cordwell 1973). Its distance has been estimated in a number of studies.Herbst & Turner (1976) used star counts to determine a distance of 1.5 - 2.0 kpc, Neckelet al. (1985) used radio data to suggest a distance of 1.5±0.5 kpc, Turner (1986a) usedstar counts to derive a distance of 2.5±0.2 kpc, and Neckel & Staude (1990) usedphotometry of foreground stars to suggest a distance of 2.0±0.3 kpc. See also the

25

Figure 20. The small cloud L810 as seen on the blue Digitized Sky Survey.

Figure 21. The small cloud L810 as observed at 850µm. The ellipse indicatesthe IRAS 19433+2743 source, filled squares are bright NIR sources, and the filledtriangle is an H2O maser. From Codella et al. (2006).

26

discussion in Hilton & Lahulla (1995). Turner (1986a) and Xie & Goldsmith (1990)noted that L810 is likely to be a member of the Vul OB1 association, which is locatedat about 2.3 kpc (e.g. Turner 1981), and further noted that it is one of a group ofcometary dark clouds with similar radial velocities and heads pointing toward the centerof Vul OB1 (see also Figure 3 of Turner 1986a). Subsequent authors have adopted eithera distance of 2.0 or 2.5 kpc. At such a large distance, L810 can hardly be classified asa globule, but rather must be considered a small cloud.

Herbst & Turner (1976) noted that at least one star towards L810 is surroundedby a reflection nebula (Figure 20). Neckel et al. (1985) used millimeter observationsto detect a warm NH3 core towards the center of L810, associated with a nebulousstar (their no. 7) that is also a bright near-infrared source. Turner (1986b) noted thatstar 7 has varied by at least 2 magnitudes. In a follow-up study, Neckel & Staude (1990)found that star 7 and three other stars may have Hα emission, and suggested that a dozenstars could be associated with the cloud. Scarrott et al. (1991) obtained a polarizationmap of L810 and showed that star 7 is not the illuminator of the reflection nebula,which they instead attribute to an embedded source, L810-IRS, and they questionedthe suggestion by Neckel & Staude that many young stars are illuminating the globule.In a near-infrared study of L810, Yun et al. (1993) detected the illuminating sourceL810-IRS which they identify with IRAS 19433+2743, the only IRAS source withinthe optical core of L810. Xie & Goldsmith (1990) found a bipolar molecular outflow,which was further mapped by Yun & Clemens (1994) and Clemens et al. (1996), whofound that the outflow is offset by about 30′′ to the west from the IRAS position. Massiet al. (2004) searched for infrared shocked emission in L810, but did not detect any,indicating that early suggestions that a major jet is present in L810 are incorrect.

Huard et al. (2000) presented 450µm and 850µm of L810, and found a clumpyring-like structure of cool dust, with two principal sources, SMM 1 and SMM 2. SMM 1is a bright extended submillimeter source broadly coincident with IRAS 19433+2743,with L810-IRS, and with star 7. SMM 2 is fainter, located about 45′′ southwest ofSMM 1, and no optical or near-infrared sources are found in this direction, suggestingthat SMM 2 may be a Class 0 source. An H2O maser found by Neckel et al. (1985)is located close to SMM 2. Codella et al. (2006) also observed L810 at 450µm and850µm, and found two more, fainter submillimeter sources, SMM 3 and SMM 4 (seeFigure 21), and noted that SMM 1 consists of two sources. They additionally mappedthe region in CO (3-2) and noted that several molecular outflows appear to be present,with a complex distribution of high-velocity gas mostly towards the SMM 2, 3, and 4region.

Yun et al. (1996) and Moreira et al. (1997) found three VLA radio continuumsources towards L810, but their nature and association with the submm sources areunclear.

Acknowledgements. I am thankful to the referee, Tyler Bourke, for a criticalreading and helpful comments. This research has made use of the SIMBAD database,operated at CDS, Strasbourg, France, and of NASA’s Astrophysics Data System Bib-liographic Services. BR was supported in part by the NASA Astrobiology Instituteunder Cooperative Agreement No. NNA04CC08A and by the NSF through grantsAST-0507784 and AST-0407005.

27

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