Conditions for thermal instability in the Galactic Centre mini-spiral region

0434721 - ASÚ 2015 RIV GB eng J - Journal Article
Rózanska, A. - Czerny, B. - Kunneriath, Devaky - Adhikari, T. P. - Karas, Vladimír - Moscibrodzka, M.
Conditions for thermal instability in the Galactic Centre mini-spiral region.
Monthly Notices of the Royal Astronomical Society. Roč. 445, č. 4 (2014), s. 4385-4394. ISSN 0035-8711. E-ISSN 1365-2966
R&D Projects: GA ČR(CZ) GC13-00070J; GA MŠMT(CZ) LH14049
Institutional support: RVO:67985815
Keywords : black holes * accretion discs * galactic centre
Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Impact factor: 5.107, year: 2014

We explore the conditions for thermal instability to operate in the mini-spiral region of the Galactic Centre (Sgr A*), where both hot and cold media are known to coexist. The photoionization Cloudy calculations are performed for different physical states of plasma.We neglect the dynamics of the material and concentrate on studying the parameter ranges where thermal instability may operate, taking into account the past history of Sgr A*’s bolometric luminosity. We show that thermal instability does not operate at the present very low level of Sgr A* activity. The instability enhances the clumpiness of the mini-spiral medium and creates the possibility for episodes of enhanced accretion of cold clumps towards Sgr A*. The mechanism determines the range of masses and sizes of clouds; under the conditions of Sgr A*, the likely values are 1–102 M-circle for the cloud’s typical mass.
Permanent Link: http://hdl.handle.net/11104/0238771