Evidence for CO depletion in the inner regions of gas-rich protoplanetary disks

Free access article

Issue		A&A Volume 500, Number 3, June IV 2009


Page(s)		1137 - 1141
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361/200811148
Published online		29 April 2009

A&A 500, 1137-1141 (2009)
DOI: 10.1051/0004-6361/200811148

Evidence for CO depletion in the inner regions of gas-rich protoplanetary disks

G. van der Plas^{1, 2}, M. E. van den Ancker¹, B. Acke³, A. Carmona^{4, 5}, C. Dominik^{2, 6}, D. Fedele⁷, and L. B. F. M. Waters^{2, 3}

¹ European Southern Observatory, Karl-Schwarzschild-Str.2, 85748 Garching bei München, Germany
² Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
e-mail: g.vanderplas@uva.nl
³ Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁴ ISDC Data Centre for Astrophysics, Ch. d'Ecogia 16, 1290 Versoix, Switzerland
⁵ Observatoire de Genève, Ch. des Maillettes 51, 1290 Sauverny, Switzerland
⁶ Institute for Astrophysics, Radbout University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
⁷ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Received 13 October 2008 / Accepted 17 April 2009

Abstract
Aims. We investigate the physical properties and spatial distribution of Carbon Monoxide (CO) gas in the disks around the Herbig Ae/Be stars HD 97048 and HD 100546.
Methods. Using high-spectral-resolution 4.588-4.715 $\mu$ m spectra containing fundamental CO emission taken with CRIRES on the VLT, we probe the circumstellar gas and model the kinematics of the emission lines. By using spectro-astrometry on the spatially resolved targets, we constrain the physical size of the emitting regions in the disks.
Results. We resolve, spectrally and spatially, the emission of the ¹³CO v(1-0) vibrational band and the ¹²CO v = 1-0, v = 2-1, v = 3-2 and v = 4-3 vibrational bands in both targets, as well as the ¹²CO v = 5-4 band in HD 100546. Modeling of the CO emission with a homogeneous disk in Keplerian motion, yields a best fit with an inner and outer radius of the CO emitting region of 11 and ${\geq}$ 100 AU for HD 97048. HD 100546 is not fit well with our model, but we derive a lower limit on the inner radius of 8 AU. The fact that gaseous [OI] emission was previously detected in both targets at significantly smaller radii suggests that CO may be effectively destroyed at small radii in the surface layers of these disks.

Key words: circumstellar matter -- stars: pre-main sequence -- stars: individual: HD 97048 -- stars: individual: HD 100546 -- planetary systems: protoplanetary disks

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