Rotating black holes in the Hernquist galactic halo and its accretion disk luminosity

TL;DR

This paper models rotating black holes within Hernquist galactic halos, analyzing their accretion disk luminosity and finding dark matter's influence on disk properties is minimal, especially for high-spin black holes.

Contribution

It constructs a rotating black hole metric in a dark matter halo using the Newman-Janis algorithm and studies its accretion disk properties, extending previous static models.

Findings

Dark matter has minimal impact on disk luminosity.

High-spin black holes show negligible differences from Kerr black holes.

Dark matter effects are harder to detect in astrophysical black holes with large spin.

Abstract

Static, spherically symmetric black holes immersed in a dark matter halo with a Hernquist-type density profile have been derived by Cardoso et. al. in Ref. \redcite{Cardoso:2021wlq}. Using the Newman-Janis algorithm, we construct the metric for a stationary and axially symmetric rotating black hole in this environment. Then, we obtain the electromagnetic properties of thin accretion disks around such rotating black holes by utilizing the steady-state Novikov-Thorne model, and study the effects of spin parameter and halo compactness parameter on the disk properties. Finally, by comparison the results of the rotating Cardoso black hole with that of Kerr black hole in the absence of dark matter, we find that the presence of dark matter can not significantly affect the disk properties and thus for astrophysical black holes with large spin parameter, the distinction of rotating Cardoso black holes becomes more difficult than the Kerr black hole.