Time Evolution of the 3-D Accretion Flows: Effects of the Adiabatic Index and Outer Boundary Condition

Abstract

We study a slightly rotating accretion flow onto a black hole, using the fully three dimensional (3-D)numerical simulations. We consider hydrodynamics of an inviscid flow, assuming a spherically symmetric density distribution at the outer boundary and a small, latitude-dependent angular momentum. We investigate the role of the adiabatic index and gas temperature, and the flow behaviour due to non-axisymmetric effects. Our 3-D simulations confirm axisymmetric results: the material that has too much angular momentum to be accreted forms a thick torus near the equator and the mass accretion rate is lower than the Bondi rate. In our previous study of the 3-D accretion flows, for gamma=5/3, we found that the inner torus precessed, even for axisymmetric conditions at large radii. The present study shows that the inner torus precesses also for other values of the adiabatic index: gamma=4/3, 1.2 and 1.01. However, the time for the precession to set increases with decreasing gamma. In particular, for gamma=1.01 we find that depending on the outer boundary conditions, the torus may shrink substantially due to the strong inflow of the non-rotating matter and the precession will have insufficient time to develop. On the other hand, if the torus is supplied by the continuous inflow of the rotating material from the outer radii, its inner parts will eventually tilt and precess, as it was for the larger gamma's.

19 pages, 19 figures; accepted to ApJ; version with full resolution figures may be downloaded from http://users.camk.edu.pl/agnes/publ_en.html

References in corpus (6)

• Global General Relativistic MHD Simulation of a Tilted Black-Hole Accretion Disk
• Instabilities in the time-dependent neutrino disc in Gamma-Ray Bursts
• Warping and precession in galactic and extragalactic accretion disks
• The Structures of Distant Galaxies - II: Diverse Galaxy Structures and Local Environments at z = 4-6; Implications for Early Galaxy Assembly
• Nonaxisymmetric Effects in the Black Hole Accretion Inviscid Hydrodynamics: Formation and Evolution of a Tilted Torus
• Time variability of accretion flows: effects of the adiabatic index and gas temperature

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