Volume 373, Number 2, July II 2001
|Page(s)||641 - 656|
|Section||Interstellar and circumstellar matter|
|Published online||15 July 2001|
On the gas temperature in circumstellar disks around A stars
Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands
Corresponding author: I. Kamp, firstname.lastname@example.org
Accepted: 2 May 2001
In circumstellar disks or shells it is often assumed that gas and dust temperatures are equal where the latter is determined by radiative equilibrium. This paper deals with the question whether this assumption is applicable for tenuous circumstellar disks around young A stars. In this paper the thin hydrostatic equilibrium models described by Kamp & Bertoldi ([CITE]) are combined with a detailed heating/cooling balance for the gas. The most important heating and cooling processes are heating through infrared pumping, heating due to the drift velocity of dust grains, and fine structure and molecular line cooling. Throughout the whole disk gas and dust are not efficiently coupled by collisions and hence their temperatures are quite different. Most of the gas in the disk models considered here stays well below 300 K. In the temperature range below 300 K the gas chemistry is not much affected by Tgas and therefore the simplifying approximation can be used for calculating the chemical structure of the disk. Nevertheless the gas temperature is important for the quantitative interpretation of observations, like fine structure and molecular lines.
Key words: molecular processes / circumstellar matter / stars: early-type / stars: individual: Vega / stars: individual: β Pictoris / planetary systems
© ESO, 2001
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