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Equilibrium initialization and stability of three-dimensional gas discs.

Authors :
Hsiang-Hsu Wang
Klessen, Ralf S.
Dullemond, Cornelis P.
van den Bosch, Frank C.
Fuchs, Burkhard
Source :
Monthly Notices of the Royal Astronomical Society. Sep2010, Vol. 407 Issue 2, p705-720. 16p. 4 Color Photographs, 1 Chart, 6 Graphs.
Publication Year :
2010

Abstract

We present a new systematic way of setting up galactic gas discs based on the assumption of detailed hydrodynamic equilibrium. To do this, we need to specify the density distribution and the velocity field which supports the disc. We first show that the required circular velocity has no dependence on the height above or below the mid-plane so long as the gas pressure is a function of density only. The assumption of discs being very thin enables us to decouple the vertical structure from the radial direction. Based on that, the equation of hydrostatic equilibrium together with the reduced Poisson equation leads to two sets of second-order non-linear differential equations, which are easily integrated to set up a stable disc. We call one approach ‘density method’ and the other one ‘potential method’. Gas discs in detailed balance are especially suitable for investigating the onset of the gravitational instability. We revisit the question of global, axisymmetric instability using fully three-dimensional disc simulations. The impact of disc thickness on the disc instability and the formation of spontaneously induced spirals is studied systematically with or without the presence of the stellar potential. In our models, the numerical results show that the threshold value for disc instability is shifted from unity to 0.69 for self-gravitating thick discs and to 0.75 for combined stellar and gas thick discs. The simulations also show that self-induced spirals occur in the correct regions and with the right numbers as predicted by the analytic theory. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00358711
Volume :
407
Issue :
2
Database :
Academic Search Index
Journal :
Monthly Notices of the Royal Astronomical Society
Publication Type :
Academic Journal
Accession number :
53322850
Full Text :
https://doi.org/10.1111/j.1365-2966.2010.16942.x