Newtonian analogue of Schwarzschild–de Sitter spacetime: Influence on the local kinematics in galaxies

Abstract

The late time accelerated expansion of the Universe demands that even in local galactic scales it is desirable to study astrophysical phenomena, particularly relativistic accretion related phenomena in massive galaxies or in galaxy mergers and the dynamics of the kiloparsecs-scale structure and beyond, in the local galaxies in Schwarzschild--de Sitter (SDS) background, rather than in Schwarzschild or Newtonian paradigm. Owing to the complex and nonlinear character of the underlying magnetohydrodynamical equations in general relativistic (GR) regime, it is quite useful to have a Newtonian analogous potential containing all the important GR features that allows us to treat the problem in Newtonian framework for study of accretion and its related processes. From the principle of conserved Hamiltonian of the test particle motion, here, a three dimensional Newtonian analogous potential has been obtained in spherical geometry corresponding to SDS/Schwarzschild--anti--de Sitter spacetime, that reproduces almost all of the GR features in its entirety with remarkable accuracy. The derived potential contains an explicit velocity dependent term of the test particle that renders an approximate relativistic modification of Newtonian-like potential. The complete orbital dynamics around SDS geometry and the epicyclic frequency corresponding to SDS metric have been extensively studied in the Newtonian framework using the derived potential. Applying the derived analogous potential it is found that the current accepted value of $\mathrm{\ensuremath{\Lambda}}\ensuremath{\sim}{10}^{\ensuremath{-}56}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$ moderately influences both sonic radius as well as Bondi accretion rate, especially for spherical accretion with smaller values of adiabatic constant and temperature, which might have interesting consequences on the stability of accretion disk in active galactic nuclei/radio galaxies.