Structure of the DM Tau Outer Disk: Probing the vertical kinetic temperature gradient

¹ Institut d'Astrophysique Spatiale, UMR 8617, Bât. 121, Campus Paris XI, 91405 Orsay, France
² Laboratoire d'Astrophysique de l'Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
³ Institut de Radio Astronomie Millimétrique, 300 Rue de la Piscine, 38406 Saint Martin d'Hères, France

Corresponding author: E. Dartois, emmanuel.dartois@ias.u-psud.fr

Received: 20 August 2002
Accepted: 6 November 2002

Abstract

We use high angular and spectral resolution ( & 0.1 km s^-1) images in ,  ,  and   coming from the IRAM interferometer to probe the vertical temperature distribution in the disk of DM Tau. We investigate here a new method based on the different opacities of the CO isotopomers to sample the temperature disk structure at various vertical scales inside the disk. Typically, the  transitions are sampling at 2–4 scale heights, while the  data are more likely tracing 1 scale height for the –1, and the disk mid-plane for the –0 line. At the disk scale at which the IRAM observations are sensitive (–60 AU), the analysis reveals a vertical temperature gradient. The outer layers where τ(  are warmer ( K) than the inner layers probed by  and  data (–20 K). These findings are consistent with the structure expected for flared irradiated disks around TTauri stars. We also observe that the outer radius of the disk is smaller in  and  than in . These differences in truncation radius are in agreement with photodissociation effects. We also note that the dynamical mass determination from CO is weakly affected by the temperature gradient.