Accretion Dynamics in SdS Space

Abstract

the role of the gravitational powerhouse of gigantic scale in AGN. The accretion process for such a black hole may be studied using general relativistic as well as post Newtonian scheme for various possible flow geometries with different equation of states of the accreted matter. For the sake of simplicity, hydro-dynamical flow models are generally adopted to get an analytical estimate for those accretion process. In our work, accretion process over a region far beyond the dimension of a single galaxy by a much more massive object (» 10 18 Mfl, a cluster of galaxies or a possible super-giant black hole) has been studied where the large scale feature of the space-time structure of the Universe may be relevant. In the non-rotating limit of the accreting black-hole with accelerated expansion of the Universe, Schwarzschild-de Sitter (SdS) space is chosen to be a suitable one. Pseudo-Newtonian potential describing the gravitational field of static and spherically symmetric black holes in the Universe with a repulsive cosmological constant, i.e. for SdS space, has been recently introduced by Stuchlik and Kovar. Using this potential, here we have studied the phase topology of the flow and also the possibility of formation of stationary shocks both in adiabatic and isothermal limits in accretion discs. In AGN, the existence of stationary shock is believed to be a plausible explanation of the extremely hot annular region there. In our study, in adiabatic (and in isothermal) cases, a significant region of parameter space allow shock formation and those regions shift in comparison with the same for Schwarzschild case due to the effect of cosmological constant in SdS space.