Jets from young stars

Mundt, R.; Fried, J. W.

doi:10.1086/184155

Cited by 291 publications

(199 citation statements)

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“…In particular, Davis et al (2003) do not detect any [Fe II] emission within 1 from the source, suggesting a jet origin for the [Fe II] emission. DG Tau B has an edge-on disk and a bipolar jet detected in the optical (Mundt & Fried 1983;Eislöffel & Mundt 1998) and radio (Rodriguez et al 1995). The jet is oriented perpendicular to the disk.…”

Section: Discussionmentioning

confidence: 99%

Searching for gas emission lines inSpitzerInfrared Spectrograph (IRS) spectra of young stars in Taurus

Baldovin-Saavedra

Audard

Güdel

et al. 2011

A&A

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Context. Our knowledge of circumstellar disks has traditionally been based on studies of dust. However, gas dominates the disk mass and its study is key to our understanding of accretion, outflows, and ultimately planet formation. The Spitzer Space Telescope provides access to gas emission lines in the mid-infrared, providing crucial new diagnostics of the physical conditions in accretion disks and outflows. Aims. We seek to identify gas emission lines in mid-infrared spectra of 64 pre-main-sequence stars in Taurus. Using line luminosities and other known star-disk-outflow parameters, we aim to identify correlations that will help to constrain gas heating, excitation mechanisms, and the line formation. Methods. We have based our study on Spitzer observations using the Infrared Spectrograph (IRS), mainly with the high-resolution modules. Line luminosities (or 3σ upper limits) have been obtained by fitting Gaussian profiles to the lines. We have further searched for correlations between the line luminosities and different parameters related to the star-disk system. Results. We have detected H 2 (17.03, 28.22 μm) emission in 6 objects, [Ne II] (12.81 μm) emission in 18 objects, and [Fe II] (17.93, 25.99 μm) emission in 7 objects. [Ne II] detections are found primarily in Class II objects. The luminosity of the [Ne II] line (L NeII ) is in general higher for objects known to drive jets than for those without known jets, but the two groups are not statistically distinguishable. L NeII is correlated with X-ray luminosity, but for Class II objects only. L NeII is also correlated with disk mass and accretion rate when the sample is divided into high and low accretors. Furthermore, we find correlations of L NeII with mid-IR continuum luminosity and with luminosity of the [O I] (6300 Å) line, the latter being an outflow tracer. L [FeII] correlates withṀ acc . No correlations were found between L H 2 and several tested parameters. Conclusions. Our study reveals a general trend toward accretion-related phenomena as the origin of the gas emission lines. Shocks in jets and outflowing material are more likely to play a significant role than shocks in infalling material. The role of X-ray irradiation is less prominent but still present for [Ne II], in particular for Class II sources, while the lack of correlation between [Fe II] and [Ne II] points toward different emitting mechanisms.

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Section: Discussionmentioning

confidence: 99%

Searching for gas emission lines inSpitzerInfrared Spectrograph (IRS) spectra of young stars in Taurus

Baldovin-Saavedra

Audard

Güdel

et al. 2011

A&A

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“…Support for an extended MHD disk wind is most evident in the bright and well-studied jet HH 158 from the actively accreting T Tauri star DG Tauri (Mundt & Fried 1983). An onion-like structure is observed within 500 AU of the star in optical forbidden emission lines, with faster gas nested inside slower material (Lavalley-Fouquet et al 2000;Bacciotti et al 2000).…”

Section: Introductionmentioning

confidence: 98%

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Agra-Amboage

Dougados

Cabrit

et al. 2011

A&A

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Context. The origin of protostellar jets as well as their impact on the regulation of angular momentum and the inner disk physics are still crucial open questions in star formation. Aims. We aim to test the different proposed ejection processes in T Tauri stars through high-angular resolution observations of forbidden-line emission from the inner DG Tauri microjet. Methods. We present spectro-imaging observations of the DG Tauri jet obtained with SINFONI/VLT in the lines of [Fe ii]λ1.64 μm, 1.53 μm with 0. 15 angular resolution and R = 3000 spectral resolution. We analyze the morphology and kinematics, derive electronic densities and mass-flux rates and discuss the implications for proposed jet launching models. Results. (1) We observe an onion-like velocity structure in [Fe ii] in the blueshifted jet, similar to that observed in optical lines. Highvelocity (HV) gas at -200 km s −1 is collimated inside a half-opening angle of 4 • and medium-velocity (MV) gas at -100 km s −1 in a cone with an half-opening angle 14.• (2) Two new axial jet knots are detected in the blue jet, as well as a more distant bubble with corresponding counter-bubble. The periodic knot ejection timescale is revised downward to 2.5 yrs. (3) The redshifted jet is detected only beyond 0. 7 from the star, yielding revised constraints on the disk surface density. (4) From comparison to [O i] data we infer iron depletion of a factor 3 at high velocities and a factor 10 at speeds below -100 km s −1 . (5) The mass-fluxes in each of the medium and high-velocity components of the blueshifted lobe are 1.6 ± 0.8 × 10 −8 M yr −1 , representing 0.02−0.2 of the disk accretion rate. Conclusions. The medium-velocity conical [Fe ii] flow in the DG Tau jet is too fast and too narrow to trace photo-evaporated matter from the disk atmosphere. Both its kinematics and collimation cannot be reproduced by the X-wind, nor can the "conical magnetospheric wind". The level of Fe gas phase depletion in the DG Tau medium-velocity component also rules out a stellar wind and a cocoon ejected sideways from the high-velocity beam. A quasi-steady centrifugal MHD disk wind ejected over 0.25−1.5 AU and/or episodic magnetic tower cavities launched from the disk appear as the most plausible origins for the [Fe ii] medium velocity component in the DG Tau jet. The same disk wind model can also account for the properties of the high-velocity [Fe ii] flow, although alternative origins in magnetospheric and/or stellar winds cannot be excluded for this component.

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“…Early studies of YSOs comparing the PA of the linear polarization and the direction of the jets, indicated that the jets are aligned preferentially perpendicular (Mundt & Fried 1983). Single scattering in an optically thin disk (Brown & McLean 1977) results in a PA perpendicular to the direction of the major axis of the disk projected onto the plane of the sky (hereinafter, the disk PA).…”

Section: Introductionmentioning

confidence: 99%

Near infrared polarimetry of a sample of YSOs

Pereyra

Girart

Magalhães

et al. 2009

A&A

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Aims. Our goal is to study the physical properties of the circumstellar environment of young stellar objetcs (YSOs). In particular, the determination of the scattering mechanism can help us to constrain the optical depth of the disk and/or envelope in the near infrared. Methods. We used the IAGPOL imaging polarimeter along with the CamIV infrared camera at the LNA observatory to obtain near infrared polarimetry measurements in the H band of a sample of optically visible YSOs, namely, eleven T Tauri stars and eight Herbig Ae/Be stars. An independent determination of the disk (or jet) orientation was obtained for twelve objects from the literature. The circumstellar optical depth could then be estimated by comparing the integrated polarization position angle (PA) with the direction of the major axis of the disk projected onto the plane of the sky. Optically thin disks have, in general, a polarization PA that is perpendicular to the disk plane. In contrast, optically thick disks have polarization PAs parallel to the disks. Results. Among the T Tauri stars, three are consistent with having optically thin disks (AS 353A, RY Tau and UY Aur) and five with optically thick disks (V536 Aql, DG Tau, DO Tau, HL Tau and LkHα 358). Among the Herbig Ae/Be stars, two stars exhibit evidence of optically thin disks (Hen 3-1191 and VV Ser) and two of optically thick disks (PDS 453 and MWC 297). Our results seem consistent with optically thick disks at near infrared bands, which are more likely to be associated with younger YSOs. Marginal evidence of polarization reversal is found in RY Tau, RY Ori, WW Vul, and UY Aur. In the first three cases, this feature can be associated with the UXOR phenomenon. Correlations with the IRAS colors and the spectral index yielded evidence of an evolutionary segregation in which the disks tend to be optically thin when they are older.

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Jets from young stars

Cited by 291 publications

References 0 publications

Searching for gas emission lines inSpitzerInfrared Spectrograph (IRS) spectra of young stars in Taurus

Searching for gas emission lines inSpitzerInfrared Spectrograph (IRS) spectra of young stars in Taurus

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Near infrared polarimetry of a sample of YSOs

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