Observational properties of rigidly rotating dust configurations

TL;DR

This paper investigates the observational signatures of rigidly rotating dust solutions in Einstein's equations, exploring their potential as alternatives to black holes in galactic centers and analyzing differences in accretion disk emissions.

Contribution

It introduces exact solutions for rotating dust configurations and examines their observational properties, proposing they could mimic black holes in astrophysical observations.

Findings

Differences in accretion disk emission spectra compared to black holes.

Potential to distinguish these solutions via iron Kα line shape.

Current X-ray missions may not detect these differences.

Abstract

We study the observational properties of a class of exact solutions of Einstein's field equations describing stationary, axially symmetric, rigidly rotating dust (i.e. non interacting particles). We ask the question whether such solutions can describe astrophysical rotating dark matter clouds near the center of galaxies and we probe the possibility that they may constitute an alternative to supermassive black holes at the center of galaxies. We show that light emission from accretion disks made of ordinary baryonic matter in this space-time has several differences with respect to the emission of light from similar accretion disks around black holes. The shape of the iron K$\alpha$ line in the reflection spectrum of accretion disks can potentially distinguish this class of solution from the Kerr metric, but this may not be possible with current X-ray missions.