A 20,000 [ITAL]M[/ITAL][TINF]⊙[/TINF] Black Hole in the Stellar Cluster G1

This is the authors' abstract. We don't add key points for this paper.

We present the detection of a 2.0 × 10 4 M ☉ black hole (BH) in the stellar cluster G1 (Mayall II), based on data taken with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope . G1 is one of the most massive stellar clusters in M31. The central velocity dispersion (25 km s -1 ) and the measured BH mass of G1 place it on a linear extrapolation of the correlation between BH mass and bulge velocity dispersion established for nearby galaxies. The detection of a BH in this low-mass stellar system suggests that (1) the most likely candidates for seed massive BHs come from stellar clusters, (2) there is a direct link between massive stellar clusters and normal galaxies, and (3) the formation process of both bulges and massive clusters is similar because of their concordance in the M • -σ relation. Globular clusters in our Galaxy should be searched for central BHs.