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On the origin of Ne [II] emission in young stars: mid-infrared and optical observations with the Very Large Telescope

Baldovin-Saavedra, C. and Audard, M. and Carmona, A. and Guedel, M. and Briggs, K. and Rebull, L. M. and Skinner, S. L. and Ercolano, B. (2012) On the origin of Ne [II] emission in young stars: mid-infrared and optical observations with the Very Large Telescope. Astronomy and Astrophysics, 543 . Art. No. A30. ISSN 0004-6361.

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Context. The [Ne II] line 12.81 μm was proposed to be a good tracer of gas in the environments of proto-planetary disks; its origin is explained by different mechanisms: jets in outflows, photo-evaporative disk winds driven by stellar X-rays/EUV or by the X-ray irradiated proto-planetary disk atmosphere. Previous Spitzer studies gave hints toward the neon emitting mechanism by exploring correlations between the line luminosity and properties of the star-disk system. These studies concluded that the origin of the emission is likely related to accretion and outflows, with some influence from X-rays. Aims. We provide direct constraints on the origin of the [Ne II] emission using high-spatial and spectral resolution observations that allow us to study the kinematics of the emitting gas. In addition we compare the [Ne II] line with optical forbidden lines. Methods. We obtained high-resolution ground-based observations with VISIR-VLT for 15 stars and UVES-VLT for three of them. The stars were chosen for having bright neon emission lines detected with Spitzer/IRS. The velocity shifts and profiles are used to disentangle the different emitting mechanisms producing the [Ne II] line. A comparison between results from this study and previous high-resolution studies is also presented. Results. The [Ne II] line was detected in seven stars, among them the first confirmed detection of [Ne II] in a Herbig Be star, V892 Tau. In four cases, the large blueshifted lines indicate an origin in a jet. In two stars, the small shifts and asymmetric profiles indicate an origin in a photo-evaporative wind. CoKu Tau 1, seen close to edge-on, shows a spatially unresolved line centered at the stellar rest velocity, although cross-dispersion centroids move within 10 AU from one side of the star to the other as a function of wavelength. The line profile is symmetric with wings extending up to ~±80 km s-1. The origin of the [Ne II] line is unclear and could either be due to the bipolar jet or to the disk. For the stars with VLT-UVES observations, in several cases, the optical forbidden line profiles and shifts are very similar to the profile of the [Ne II] line, suggesting that the lines are emitted in the same region. A general trend observed with VISIR is a lower line flux when compared with the fluxes obtained with Spitzer. We found no correlation between the line full-width at half maximum and the line peak velocity. The [Ne II] line remains undetected in a large part of the sample, an indication that the emission detected with Spitzer in those stars is likely extended.

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Rebull, L. M.0000-0001-6381-515X
Additional Information:© 2012 The European Southern Observatory (ESO). Received: 25 October 2011, Accepted: 9 May 2012. Published online 22 June 2012. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. We thank the referee, Dr. G. Herczeg, for thoughtful, and detailed comments that improved the manuscript. C.B.-S., M.A., and A.C. acknowledge support from the Swiss National Science Foundation (grants PP002-110504 and PP00P2-130188). The authors thank A. Mueller for providing the authors high-resolution synthetic spectra of low-mass stars, and ESO staff for performing UVES observations in service mode.
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:stars: pre-main sequence, stars: formation, ISM: jets and outflows, infrared: stars, protoplanetary disks
Record Number:CaltechAUTHORS:20150817-124809417
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Official Citation:On the origin of [Ne II] emission in young stars: mid-infrared and optical observations with the Very Large Telescope A30 C. Baldovin-Saavedra, M. Audard, A. Carmona, M. Güdel, K. Briggs, L. M. Rebull, S. L. Skinner and B. Ercolano Published online: 22 June 2012 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59611
Deposited By: Luisa Rebull
Deposited On:18 Aug 2015 17:46
Last Modified:03 Oct 2019 08:48

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