Thermal stability of self-gravitating, optically thin accretion disks

Citation
G. Bertin et G. Lodato, Thermal stability of self-gravitating, optically thin accretion disks, ASTRON ASTR, 370(1), 2001, pp. 342-350
Citations number
26
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY AND ASTROPHYSICS
ISSN journal
0004-6361 → ACNP
Volume
370
Issue
1
Year of publication
2001
Pages
342 - 350
Database
ISI
SICI code
0004-6361(200104)370:1<342:TSOSOT>2.0.ZU;2-O
Abstract
In the dynamics of accretion disks, the presence of collective effects asso ciated with the self-gravity of the disk is expected to affect not only the momentum transport, but also the relevant energy balance equations, which could differ substantially from the non-self-gravitating case. Here we foll ow the model that, when the disk is sufficiently cold, the stirring due to Jeans-related instabilities acts as a source of effective heating. The corr esponding reformulation of the energy equations allows us to: (i) demonstra te how self-regulation can be established, so that the stability parameter Q is maintained close to a threshold value, with weak dependence on radius; (ii) rediscuss the opacity properties in the self-gravitating regime. In p articular, Re show that, if cooling is dominated by bremsstrahlung, an opti cally thin stationary accretion solution is thermally stable, even in the n on-advective case, provided the disk is self-gravitating. The details of th e cooling function have little effect on the structure of such accretion di sk, which is in any case induced by self-gravity to self-regulate. This con dition of self-gravitating accretion is expected to be appropriate for the outer regions of many disks of astrophysical interest. With the reformulati on of the energy equations described in this paper, me have also secured: ( iii) a starting point for the study of the emission properties of self-grav itating- accretion disks; (iv) a tool to analyze the structure of the trans ition region, where the disk becomes self-gravitating.