Observations of the Chemistry in Circumstellar Disks

Abstract

Circumstellar disks around classical T Tauri stars have still large amounts of primary molecular gas and dust, which may evolve to form planetary systems. Although it is the remnant of the parental cloud, the gas component shows significant chemical evolution. Fundamental disk properties (kinematics, size, temperature profile) can be derived from observations of CO lines with mm arrays. Less abundant molecules have been discovered with the IRAM 30-m telescope, in the DM Tau and GG Tau disks. Despite the high depletion factors which are measured with respect to the nearby Taurus cloud, these molecules allow independent measurements of the disk density. These observations provide an overview of the properties of young (a few Myr) proto-planetary disks around low-mass stars as seen by current mm instruments.