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

Baldovin-Saavedra, C. and Audard, M. and Güedel, M. and Rebull, L. M. and Padgett, D. L. and Skinner, S. L. and Carmona, A. and Glauser, A. M. and Fajardo-Acosta, S. B. (2011) Searching for gas emission lines in Spitzer Infrared Spectrograph (IRS) spectra of young stars in Taurus. Astronomy and Astrophysics, 528 . Art. No. A22. ISSN 0004-6361.

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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 with Ṁ_(acc). No correlations were found between L_(H2) 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.

Item Type:Article
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URLURL TypeDescription
Rebull, L. M.0000-0001-6381-515X
Padgett, D. L.0000-0001-5334-5107
Fajardo-Acosta, S. B.0000-0001-9309-0102
Additional Information:© 2011 ESO. Received 19 August 2010. Accepted 14 January 2011. Published online 21 February 2011. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. C.B-S., M.A., and A.C. acknowledge support from the Swiss National Science Foundation (grants PP002-110504 and PP00P2-130188). We thank Fred Lahuis for useful discussion on the data reduction, Maria Suveges for insightful discussion on bootstrap techniques, and an anonymous referee for suggestions and comments that improved the manuscript.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)PP002-110504
Swiss National Science Foundation (SNSF)PP00P2-130188
Subject Keywords:ISM: jets and outflows; infrared: stars; protoplanetary disks; stars: formation; stars: pre-main sequence; stars: protostars
Record Number:CaltechAUTHORS:20110413-081503573
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Official Citation:Searching for gas emission lines in Spitzer Infrared Spectrograph (IRS) spectra of young stars in Taurus A22 C. Baldovin-Saavedra, M. Audard, M. Güdel, L. M. Rebull, D. L. Padgett, S. L. Skinner, A. Carmona, A. M. Glauser and S. B. Fajardo-Acosta Published online: 21 February 2011 DOI: 10.1051/0004-6361/201015622
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23303
Deposited By: Ruth Sustaita
Deposited On:13 Apr 2011 15:45
Last Modified:09 Mar 2020 13:18

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