An upper limit on the mass of the black hole in Ursa Minor dwarf galaxy

TL;DR

This study uses N-body simulations to set an upper limit on the mass of a potential black hole in the Ursa Minor dwarf galaxy, finding it unlikely to exceed 2-3×10^4 solar masses based on observed stellar substructure.

Contribution

The paper provides the first dynamical upper limit on the black hole mass in Ursa Minor using N-body simulations, extending the M_{BH}-sigma relation to low-mass regimes.

Findings

Black hole mass in UMi is likely less than 2-3×10^4 solar masses.

Observed stellar substructure is incompatible with a more massive black hole.

The black hole may be offset from the galaxy's center.

Abstract

The well-established correlations between the mass of massive black holes (BHs) in the nuclei of most studied galaxies and various global properties of their hosting galaxy lend support to the idea that dwarf galaxies and globular clusters could also host a BH in their centers. Direct kinematic detection of BHs in dwarf spheroidal (dSph) galaxies are seriously hindered by the small number of stars inside the gravitational influence region of the BH. The aim of this Letter is to establish an upper dynamical limit on the mass of the putative BH in the Ursa Minor (UMi) dSph galaxy. We present direct N-body simulations of the tidal disruption of the dynamical fossil observed in UMi, with and without a massive BH. We find that the observed substructure is incompatible with the presence of a massive BH of (2-3)x10^4 Msun within the core of UMi. These limits are consistent with the extrapolation of the M_{BH}-sigma relation to the M_{BH}<10^6 Msun regime. We also show that the BH may be off-center with respect to the center of symmetry of the whole galaxy.