Thi, W.-F. and van Dishoeck, E. F. and Pontoppidan, K. M. and Dartois, E. (2010) Evidence for episodic warm outflowing CO gas from the intermediate-mass young stellar object IRAS 08470–4321. Monthly Notices of the Royal Astronomical Society, 406 (3). pp. 1409-1424. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20100831-093332525
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We present a R ≃ 10 000 M-band spectrum of LLN 19 (IRAS 08470−4321), a heavily embedded intermediate-mass young stellar object located in theVela molecular cloud, obtained with the Very Large Telescope (VLT)-Infrared Spectrometer And Array Camera (ISAAC). The data were fitted by a two-slab cold-hot model and a wind model. The spectrum exhibits deep broad ro-vibrational absorption lines of ^(12)CO v = 1←0 and ^(13)CO v = 1←0. A weak CO ice feature at 4.67 μmis also detected. Differences in velocity indicate that the warm gas is distinct from the cold millimetre emitting gas, which may be associated with the absorption by cooler gas (45 K). The outflowing warm gas at 300–400 K and with a mass-loss rate varying between 0.48 × 10^(−7) and 4.2 × 10^(−7) M_⊙ yr^(−1) can explain most of the absorption. Several absorption lines were spectrally resolved in subsequent spectra obtained with the VLT-Cryogenic Infrared Echelle Spectrograph (CRIRES) instrument. Multiple absorption substructures in the highresolution (R = 100 000) spectra indicate that the mass-loss is episodic with at least two major events that occurred recently (<28 yr). The discrete mass-loss events together with the large turbulent width of the gas (dv = 10–12 km s^(−1)) are consistent with the predictions of the jet-bow shock outflow and the wide-angle wind model. The CO gas/solid column density ratio of 20–100 in the line of sight confirms that the circumstellar environment of LLN 19 is warm. We also derive a ^(12)C/^(13)C ratio of 67 ± 3, consistent with previous measurements in local molecular clouds but not with the higher ratios found in the envelope of other young stellar objects.
|Additional Information:||© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 February 10. Received 2010 February 10; in original form 2009 September 30. Article first published online: 20 July 2010. Based on observations collected at the VLT of the European Southern Observatory (ESO) at La Silla and Paranal, Chile (ESO Programmes I64.I- 0605 and I79.C-0151). WFT is supported by a Scottish Universities Physics Alliance (SUPA) fellowship in astrobiology. This research is supported by the Netherlands Research School for Astronomy (NOVA) and a NWO Spinoza grant. KMP acknowledges a Hubble fellowship. The authors wish to thank the VLT staff for all their help in obtaining the observations. WFT thanks Peder Noberg for discussions on statistics and data fitting. We thank the referee for his/her useful comments and suggestions.|
|Subject Keywords:||ISM: jets and outflows; ISM: lines and bands|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||15 Sep 2010 20:17|
|Last Modified:||26 Dec 2012 12:22|
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