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

TL;DR

This paper develops a Newtonian-like potential that accurately mimics general relativistic effects in Schwarzschild-de Sitter spacetime, enabling easier analysis of galactic phenomena influenced by cosmic acceleration.

Contribution

A new three-dimensional Newtonian analogous potential for SDS spacetime is derived, capturing key GR features and facilitating studies of accretion and orbital dynamics in a Newtonian framework.

Findings

The potential reproduces GR features with high accuracy.

Cosmological constant influences sonic radius and accretion rates.

Implications for stability of accretion disks in AGNs and radio 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 an Newtonian analogous potential containing all the important GR features that allows 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 (SADS) 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 $\Lambda \sim 10^{-56} \rm cm^{-2}$ 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 AGNs/radio galaxies.