Recent discoveries of black hole (BH) candidates in Galactic and extragalactic globular clusters (GCs) have ignited interest in understanding how BHs dynamically evolve in a GC and the number of BHs (NBH) that may still be retained by today's GCs. Numerical models show that even if stellar-mass BHs are retained in today's GCs, they are typically in configurations that are not directly detectable. We show that a suitably defined measure of mass segregation (∆) between, e.g., giants and low-mass main-sequence stars, can be an effective probe to indirectly estimate NBH in a GC aided by calibrations from numerical models. Using numerical models including all relevant physics we first show that NBH is strongly anticorrelated with ∆ between giant stars and low-mass main-sequence stars. We apply the distributions of ∆ vs NBH obtained from models to three Milky Way GCs to predict the NBH retained by them at present. We calculate ∆ using the publicly available ACS survey data for 47 Tuc, M 10, and M 22, all with identified stellar-mass BH candidates. Using these measured ∆ and distributions of ∆ vs NBH from models as calibration we predict distributions for NBH expected to be retained in these GCs. For 47 Tuc, M 10, and M 22 our predicted distributions peak at NBH ≈ 20, 24, and 50, whereas, within the 2σ confidence level, NBH can be up to ∼ 150, 50, and 200, respectively.
|Original language||English (US)|
|State||Published - Dec 11 2017|
- Black holes-stars
- General-globular clusters
- Individual (47 Tuc, M 10, M 22)
- Kinematics and dynamics-globular clusters
ASJC Scopus subject areas