Stellar jetsStellar jets (I)(I)

History; Properties from observations

Highly collimated jets (ejected gas; supersonic velocities) are observed in many classes of astrophysical objects, both stellar and extragalactic (Livio, 2009):

Stellar Stellar ExtragalacticExtragalactic

Young Stellar Objects Active Galactic NucleiMassive X-Ray Binaries Gamma-Ray BurstsBlack Hole X-Ray TransientsLow Mass X-Ray BinariesSymbiotic StarsPlanetary Nebulae NucleiSupersoft X-Ray SourcesRecurrent NovaePulsars

NGC 6543NGC 6543

CrabCrab

HH HH 111111

HH 111 M 87

NGC 6543

Crab

MorphologyMorphology

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JETS AND DISKS

The emission mechanisms in the different classes of objects are very differentvery different.. Also, are very different their dimensions, densities and velocitiesdimensions, densities and velocities. Simply compare YSOs and AGNs.

However, the basic mechanism for the acceleration and collimation of the jet is likely to be the same in most if not all of the different classes of objects.

Jets most probably requires the presence of an accretion disk around the central object for the acceleration and collimation mechanism to operate.

In the case of YSOs, accretion disks are always present in those objects with jets. Clear examples are HH 30, DG Tau B, Haro 6-5B and HK Tau.

Jet OriginJet Origin

Observations indicate that the jet velocity is always of the order of the jet velocity is always of the order of the escape velocity from the central objectescape velocity from the central object.. This immediately indicates that most most of the outflow originatesof the outflow originates at the accretion disk close to the central objectclose to the central object. HST images of HH 30 and DG Tau B indeed show that the jets are emanating from the central part of the accretion disk.

OPTICAL• Herbig-Haro Objects; discovered in the early 50s• First symposium in 1983 (Bohm, ed.)• 1980s - HH objects part of bipolar outflows (Dopita; Mundt; Graham; Reipurth)• Spectroscopy; proper motion studies; modeling• 1990s - HST …

1994

Herbig & Jones 1981 Bally et al. 2002

HH 212HH 212

Wiseman, J.Wiseman, J.ApJ, 550, L87 (2001ApJ, 550, L87 (2001)

NHNH33(disk)

protostar

H2 2,12 m(NIR, K-band)

Davis et al. 1994, 2000

NEAR-IRNEAR-IR • H2 emission lines discovered in Orion; Gautier 1976• High-resolution studies of outflows from more embedded sources!• 1980s - spectroscopy; molecular shock physics (theory) • 1990s - First sub-arcsec images; high-resol. spec. (CGS4) - kinematics and excitation - numerical simulations; bows; entrainment

Calar Alto1993

UKIRT1999

(SUB)-MILLIMETRE • Broad CO lines in Orion (Kwan & Scoville 1976)• 1980s - CO surveys in the (Snell, Bally, Edwards, Lada)• 1990s - Higher-energy lines (submm @ JCMT); isotopes; shock chemistry in outflows; entrainment models• Interferometry @ Plateau de Bure, CARMA, SMA - molecular “jets”; study of massive Star-Forming regions.

Davis & Eisloeffel 1996 Gueth et al. 1998 Beltran et al. 2004

JETS FROM YSOsJETS FROM YSOs

Herbig-Haro ObjectsHerbig-Haro Objects

The history of jets from YSOs began with the discovery of the Herbig-Haro objects by George Herbig Herbig and Guillermo HaroHaro in the late 40’ s of the past century. These enigmatic objects showed rather peculiar characteristics: they were small nebulae (a few tens of arcsec in size), with an strange spectrum (very different from any known at that time) and, most intriguing, far away from any powering source.

Herbig’s Catalog (1974)

Bally et al. AJ 123, 2627 (2002)

HH 1-2

Discovered by:Discovered by:

**G.H.Herbig(1951):**G.H.Herbig(1951): The spectra of two nebulous objects near NGC 1999 (ApJ 113, 697).On a series of direct photographs taken with the Crosslyer reflector in 1946 and 1947 and centered on the diffuse nebula NGC 1999, there appear several peculiar nebulous objects. The brightest of these (referred to hereafter as "No. 1") resembles, on the best plates, a slightly diffuse star with a very short curved, nebulous "tail" extending for 5" in p.a. 52º. Its visual magnitude was estimated at the telescope to be near 16. It lies 1'.0 west and 2'.2 south of BD-6 1253, the illuminating star of NGC 1999. Object No.2, which is 0'.1 east and 4'.1 south of BD6 1253, is composed of two faint stars 9" apart, one much fainter star, and three closely associated semistellar clots of nebulosity; the entire object would be contained in a circle 20" in diameter. It is superimposed on much fainter nebulosity in the form of a ring, and slit spectrograms indicate that still feebler emission nebulosity is present over the entire field. The two brighter stars in object No.2 were estimated to be about visual magnitude 17.5.

and**G. Haro ApJ 115, 572 (1952)**G. Haro ApJ 115, 572 (1952)

In a recently published note G.H.Herbig (ApJ 113,697, 1951) reports the discovery of three peculiar nebulous objects near NGC 1999 and gives the spectroscopic description of the two brightest. The writer had independently discovered these peculiar objects, finding Ha and the [O I] lines at 6300 and 6363 in emission in the spectra of them.

First spectrophotometric study by:First spectrophotometric study by:Karl-Heinz Böhm (ApJ 123, 379, 1956)Karl-Heinz Böhm (ApJ 123, 379, 1956)

Relative intensities of the emission lines in the spectrum of the brightest Herbig-Haro Object have been determine from three spectrograms taken by Herbig in January, 1955.Therefore, the most obvious means of explaining the ionization is to assume a strong radiation field in the far ultraviolet. If the radiation is produced by radiation is produced by a "central star" (of solar dimension) in the nebulaa "central star" (of solar dimension) in the nebula, a radiation temperature of 24000° K is required to explain the observed ratio of [ O II] and [O III].

BUTBUT : :** ** Deep optical and NIR images fail to detect the embedded star (inside Deep optical and NIR images fail to detect the embedded star (inside the HH nebulosity)the HH nebulosity)( Haro, G., Minkowski, R.: 1960, The Herbig-Haro objects near NGC 1999, AJ 65, 490).

** Variability of the HH nebulosities:** Variability of the HH nebulosities:The nebulosities change their brightness, dissapear and move relative to The nebulosities change their brightness, dissapear and move relative to Field stars with a scale of time of several yrsField stars with a scale of time of several yrs

All of this goes in favour of the exciting source being located outside of All of this goes in favour of the exciting source being located outside of the HH nebulosity. the HH nebulosity.

HHs=reflection nebulae illuminated by an external sourceHHs=reflection nebulae illuminated by an external source

Strom, S. E., Grasdalen, G. L., & Strom, K. M.Strom, S. E., Grasdalen, G. L., & Strom, K. M.Infrared and optical observations of Herbig-Haro objectsApJ., 191, 111-142 (1974)

““old example”old example”

BURNHAM NEBULA (HH 255)BURNHAM NEBULA (HH 255)

Burnham Nebula was discovered by Burnham (1984)as a small nebula some arcsec to the south of T-Tau.(Burnham, S.W., Observations of Nebulae with the 36-inch refractor of the Lick Observatory, Pub. Lick Obs., 2, 1689)

From high-resolution long-slit spectra in the range 6250-6800 A Emission nebulosities around T-Tau (Böhm & Solf 1994ApJ, 430, 277).

ASSOCIATED WITH TTSASSOCIATED WITH TTS

****(Osterbrock, 1958): supersonic gas, ejected by a TTS, excites the surrounding nebula and produces the observed emission lines.

****Supersonic stellar wind interaction with the ambient gas

Radiative shock HH is createdHH is created

CATALOGS:CATALOGS:

*Herbig*Herbig (1974) ~40 objects

*Reipurth*Reipurthhttp://www.astro.umass.edu/catalogs/HHcat/HHintro.html#home

(> 1000, in progress)

Today we know that they are just either the brightest parts of the very collimated outflows or jets produced by young stellar objects or in the region of where the jet hits the surrounding medium. The characteristic spectrum is spectrum is produced in the cooling region of fast shock waves.produced in the cooling region of fast shock waves.

HH 34HH 1/ 2

A) Morphology• Bipolar with a slight difference in direction between jet and counterjet.• Extremely well collimated with small opening angles of no more than a few degrees.

Many are not perfectly straight , but show a gradual change in direction or bending.• Lengths around a fraction of a parsec, although, in some cases the jet can be

traced for several parsecs from the source. Widths between 50-500 AU.• They show a series of bright, almost equidistant, knots inside the body of the jet.

Jet propertiesJet properties

Highly collimated morphology

wiggling

HH30 jet/counterjet system[SII] CCD image

Acquired with ACAM (WHT)

HH 110HH 110

HH 270HH 270

““JETS” in ORIONJETS” in ORION

Reipurt & Bally

HH 110HH 110[SII] CCD image with [SII] CCD image with NOT/ALFOSCNOT/ALFOSC

NN

HH 270HH 270

~4 ARCMIN

Lack of exciting source? Knot

More “chaotic” morphology

Hartigan et al. Hartigan et al. (2005), AJ 130, 2197(2005), AJ 130, 2197

““curved” curved” morphology morphology +”bow-shock”+”bow-shock”

Straight Straight morphologymorphology

Terminal bow-shockTerminal bow-shock

IWS

Exciting source: YSO surounded by a circunstellar disk

NIR:NIR:H2

[FeII]

Optical:Optical:[SII]

H

9” (4,000 AU)

HH111HH111

(Orion)(Orion)(Reipurth et al. 1999)

knot

Bow-shock

Molecular OutflowsMolecular Outflows

High-velocity molecular outflows is a very common phenomenon clearly related to jets in YSOs. When both phenomena are observed, both coincide in direction and sense. They are observed in lines of many molecules, most notably in H2 and CO.

Observations

• Mostly bipolar. Wider and longer than the jet.

• Velocities in the range from a few km/s to less than a hundred.

• Sizes ranging from less than 0.1 pc to several parsecs.

• Kinematical time-scales from about 103 to 105 yr.

• Masses from a few 10-4 to several hundreds Msun.

Conclusions

• So massive that they must consist of accelerated ambient molecular

material.

• The momentum and power of the ionized jet component is usually not

enough for the required acceleration.

• An additional wide-angle wind is probably required to explain the

observed morphologies and to easy the momentum problem.

Sub and mm wvl

Optical/Nir wvl

Unified model: molecular outflow/Unified model: molecular outflow/Jet HHsJet HHs

Formation MechanismFormation Mechanism

The most likely mechanism for theThe most likely mechanism for the launching of the jet from the disk involves launching of the jet from the disk involves hydromagnetic acceleration and collimation. That is, the outflow is initially hydromagnetic acceleration and collimation. That is, the outflow is initially controlled by acontrolled by a strong magnetic field anchored to the disk and the central object.strong magnetic field anchored to the disk and the central object.