Investigating the nature of mass distribution surrounding the Galactic supermassive black hole

TL;DR

This paper explores how the distribution of dark matter or stellar mass around the Galactic Centre's supermassive black hole affects stellar orbit precession, proposing observational tests to uncover the mass environment and dark matter nature.

Contribution

It introduces a method to estimate the influence of surrounding mass on stellar orbit precession, highlighting potential observational signatures of dark matter near the SMBH.

Findings

Dark matter can slow down the precession of S2's orbit by up to 27%.

Future observations of stellar orbits can reveal the mass distribution around the SMBH.

The study provides a framework to differentiate between various dark matter scenarios.

Abstract

In the past three decades, many stars orbiting about the supermassive black hole (SMBH) at the Galactic Centre (Sgr A*) were identified. Their orbital nature can give stringent constraints for the mass of the SMBH. In particular, the star S2 has completed at least one period since our first detection of its position, which can provide rich information to examine the properties of the SMBH, and the astrophysical environment surrounding the SMBH. Here, we report an interesting phenomenon that if a significant amount of dark matter or stellar mass is distributed around the SMBH, the precession speed of the S2 stellar orbit could be `slow down' by at most 27\% compared with that without dark matter surrounding the SMBH, assuming the optimal dark matter scenario. We anticipate that future high quality observational data of the S2 stellar orbit or other stellar orbits can help reveal the actual mass distribution near the SMBH and the nature of dark matter.