Exploring the correlations between globular cluster populations and supermassive black holes in giant galaxies

Abstract

This paper presents an analysis of the correlation between the number of globular clusters (NGC) in giant galaxies and the mass of the galaxies' central supermassive black hole ( MSMBH). I construct a sample of 20 elliptical, spiral, and S0 galaxies with known SMBH masses and with accurately measured GC system properties derived from wide-field imaging studies. The coefficients of the best-fitting NGC−MSMBH relation for the early-type galaxies are consistent with those from previous work but in some cases have smaller relative errors. I examine the correlation between NGC and MSMBH for various subsamples and find that elliptical galaxies show the strongest correlation, while S0 and pseudobulge galaxies exhibit increased scatter. I also compare the quality of the fit of the numbers of metal-poor GCs versus SMBH mass and the corresponding fit for metal-rich GCs. I supplement the 20 galaxy sample with 10 additional galaxies with reliable NGC determinations but without measured MSMBH. I use this larger sample to investigate correlations between NGC and host galaxy properties like total galaxy luminosity and stellar mass, and bulge luminosity and mass. I find that the tightest correlation is between NGC and total galaxy stellar mass. This lends support to the notion that NGC and MSMBH are not directly linked but are correlated because both quantities depend on the host galaxy potential. Finally, I use the NGC−MSMBH relation derived from the 20 galaxy sample to calculate predicted MSMBH values for the 10 galaxies with accurate NGC measurements but without measured SMBH masses.