Letter to the Editor
Evidence for an inner molecular disk around massive Young Stellar Objects*
Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands e-mail: firstname.lastname@example.org
Accepted: 2 October 2004
We present observations of CO overtone bandhead emission toward four massive Young Stellar Objects (spectral type O6–B5). The high signal-to-noise ratio K-band spectra were obtained with VLT-ISAAC at a resolution km s-1, sufficient to resolve the bandheads, but not the individual J-lines. We are able to explain the shape of the lines by assuming a simple isothermal Keplerian disk model seen at different inclinations. The gas temperature ranges from 1500 to 4500 K and the CO column density is between 0.1 and cm-2. The emission probably arises within the first few astronomical units of the disk, consistent with the high gas temperature. Our results indicate that molecules can survive close to a hot star and suggest that dense ( cm-3) inner disks may be relatively common at an advanced stage of high-mass star formation.
Key words: stars: early-type, formation / circumstellar matter / molecular processes / line: profiles
© ESO, 2004