Do Globular Clusters Harbor Black Holes?

We present dynamical models for the massive globular cluster G1. The goal is to measure or place a significant upper limit on the mass of any central black hole. Whether or not globular clusters contain central massive black holes has important consequences for a variety of studies. We use new kinematic data obtained with Keck and new photometry from the Hubble Space Telescope. The Keck spectra allow us to obtain kinematics out to large radii that are required to pin down the...

The masses of supermassive black holes (SMBHs, M_BH=10^6-10^11 Msun) in the centres of galaxies are related to the host stellar spheroid mass and velocity dispersion. A key question is how these relations originate, and over which range of black hole masses they hold. It has been speculated that intermediate-mass black holes (IMBHs, M_BH=10^2-10^5 Msun) could play a fundamental role in the growth of SMBHs. A handful of IMBHs has recently been detected in Galactic globular clu...

This paper presents an analysis of the correlation between the number of globular clusters (N_GC) in giant galaxies and the mass of the galaxies' central supermassive black hole (M_SMBH). I construct a sample of 20 elliptical, spiral, and S0 galaxies with known SMBH masses and with accurately-measured globular cluster system properties derived from wide-field imaging studies. The coefficients of the best-fitting N_GC-M_SMBH relation for the early-type galaxies are consistent ...

Extremely rich populations of globular clusters, numbering ten thousand or more, surround the central giant galaxies in rich clusters. I discuss some recent spectroscopic and photometric observations of these rich globular clusters populations. In very nearby galaxy clusters, the globular cluster velocities can be used to trace the transition from the galaxy potential to the larger cluster potential. Beyond cz \approx 3000 km/s, the globulars are too faint for spectroscopic s...

Elliptical, lenticular, and early-type spiral galaxies show a remarkably tight power-law correlation between the mass M_BH of their central supermassive black hole (SMBH) and the number N_GC of globular clusters: M_BH=m*N_GC^(1.08+/-0.04) with m=1.7*10^5 solar masses. Thus, to a good approximation the SMBH mass is the same as the total mass of the globular clusters. Based on a limited sample of 13 galaxies, this relation appears to be a better predictor of SMBH mass (rms scat...

We analyze the relation between the mass of the central supermassive black hole (Mbh) and the number of globular clusters (Ngc) in elliptical galaxies and bulges as a ramification of the black hole fundamental plane, the theoretically predicted and observed multi-variable correlation between Mbh and bulge binding energy. Although the tightness of the Mbh-Ngc correlation suggests an unlikely causal link between supermassive black holes and globular clusters, such a corresponde...

We present internal velocity dispersion determinations from high-resolution spectroscopic observations of a sample of nine globular clusters in M31. Comprehensive numerical simulations are used to show that the typical uncertainty of our velocity dispersion measurements is about 5%. Using these new velocity dispersions together with structural parameters derived from HST observations, we estimate the mass-to-light ratios of these clusters and find that they are typical of tho...

We explore several correlations between various large-scale galaxy properties, particularly total globular cluster population (N_GCS), the central black hole mass (M_BH), velocity dispersion (nominally sigma_e), and bulge mass (M_dyn). Our data sample of 49 galaxies, for which both N_GC and M_BH are known, is larger than used in previous discussions of these two parameters and we employ the same sample to explore all pairs of correlations. Further, within this galaxy sample w...

Decades after the first predictions of intermediate-mass black holes (IMBHs) in globular clusters (GCs) there is still no unambiguous observational evidence for their existence. The most promising signatures for IMBHs are found in the cores of GCs, where the evidence now comes from the stellar velocity distribution, the surface density profile, and, for very deep observations, the mass-segregation profile near the cluster center. However, interpretation of the data, and, in p...

There have been increasing theoretical speculations and observational indications that certain globular clusters (GCs) could contain a sizeable population of stellar mass black holes (BHs). In this paper, we shortlist at least 29 Galactic GCs that could be hosting a subsystem of BHs (BHS). In a companion paper, we analysed results from a wide array of GC models (simulated with the MOCCA code for cluster simulations) that retained few tens to several hundreds of BHs at 12 Gyr ...