Probing dark matter distributions with the pericentre precession of the stellar orbits near the Galactic Centre black hole

TL;DR

The study addresses whether dark matter distributions near the Galactic Centre BH imprint detectable signatures on the pericentre precession of S-star orbits. It analyzes Plummer, cusp, spike, SIDM, and fuzzy DM profiles, constrains their parameters using the latest extended-mass bounds, and computes the resulting precession and sky shifts, comparing them to Schwarzschild precession. The S2 orbit is largely insensitive to DM precession, while low-eccentricity and wider orbits offer better prospects, with some stars potentially distinguishing between DM profiles using GRAVITY and the upcoming TMT. The work also evaluates modified gravity scenarios (f(R) and STVG) via the f_sp parameter and provides new constraints on a scalar-mode mass, illustrating how GC astrometry can test gravity and infer the Galaxy's central formation history.

Abstract

The Galactic Centre black hole provides a naive environment for understanding unknown matter distribution and new gravitational physics. For this stellar orbits in the nuclear star cluster are reliable probes. We investigate different dark matter mass profiles through pericentre shift of stellar orbits near the black hole. We also study capability of existing and upcoming astrometric facilities to detect dark matter induced precession and to distinguish between several dark matter profiles. Parameters of different dark matter density profiles are estimated by using the most recent upper bound on dark mass near the black hole. These profiles are then used for calculating the gravitational potential and hence the relativistic pericentre shift of both low and high eccentricity orbits of 13 S-stars. We use the recently measured deviation parameter $f_{sp}$ for investigating competition between dark matter and gravitational physics within S2's orbit. The astrometric shift of the pericentres has been calculated and compared with existing and upcoming astrometric capabilities of large and extremely large telescopes. The orbit of S2 is found to be insensitive to dark matter induced precession. Low eccentricity and wider orbits are prominent probes for measuring dark matter induced precession which is accessible to present and upcoming astrometric facilities such as Keck, GRAVITY and TMT. The existing and upcoming facilities can distinguish between different dark matter profiles for some stars and hence they posses the capability to distinguish between possible formation histories of the central region of our Galaxy.

Figures (6)

• Figure 1: Variation of density profiles (panel (a)) and mass profiles (panel (b)) with galactocentric distance. The grey vertical lines represent pericentre and apocentre of S2. The black horizontal line in panel (b) represents the $1200\ M_\odot$ bound.
• Figure 2: Variation of precession angles for different dark matter profiles as well as GR against semi-major axis.
• Figure 3: The deviation parameter $f_{sp}$ for different dark matter models as well as modified gravity models
• Figure 4: Astrometric shift caused by different dark matter profiles (vertical bars) along with astrometric capabilities of Keck, GRAVITY and TMT.
• Figure 5: The projection of the S-star orbits in the sky plane investigated in this work. Potential orbits where dark matter effects could be detectable are highlighted in color. Rest of the orbits are marked in grey. The orbit of S2 is represented by dashed line.