NOAO >   Observing Info >   Approved Programs >   2012A-0344

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Proposal Information for 2012A-0344


PI: Sean Brittain, Clemson University, sbritt@clemson.edu
Address: Physics Department, 118 Kinard Laboratory, Clemson, SC 29631, USA

CoI: Lindo Podio, Kapteyn Astronomical Inst.
CoI: Emma Whelan, Laboratoire d'Astrophysique Observatoire de Grenoble
CoI: Myriam Benisty, Laboratoire d'Astrophysique Observatoire de Grenoble
CoI: Catherine Dougados, Laboratoire d'Astrophysique Observatoire de Grenoble

Title: HI emission lines on young stars: accretion or ejection tracers? A spectro-astrometric survey with GEMINI/NIFS

Abstract: HI lines are effective probes of the hot gas in the inner star-disk region of young stars, where accretion and ejection of matter take place. Thus, they are crucial to test proposed accretion/ejection models and the disk structure. In particular, HI lines such as Pa(beta) and Br(gamma), are used as accretion tracers, based on the observed relationship between their luminosity and accretion luminosity. Recent studies, however, show that while this correlation holds for Herbig Ae, it does not hold for Herbig Be stars. Moreover, a few spectro-astrometric studies and interferometric observations indicate that Pa(beta) and Br(gamma) can be excited in the inner gaseous disk and/or at the base of a wind/jet. To clarify the origin of HI lines we propose a survey of the Pa(beta) and the Br(gamma) lines on Herbig Ae/Be stars by means of spectro-astrometry. The high angular resolution offered by GEMINI/NIFS coupled to spectro-astrometry will allow us to detect extended emission down to sub-AU scales and thus to disentangle the contributions from the inner disk, the accreting flows and the outflowing gas across the line velocity profile.


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NOAO >   Observing Info >   Approved Programs >   2012A-0344

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