The growth of supermassive black holes in pseudo-bulges, classical bulges and elliptical galaxies

Using results from structural analysis of a sample of nearly 1000 local galaxies from the Sloan Digital Sky Survey, we estimate how the mass in central black holes is distributed amongst elliptical galaxies, classical bulges and pseudo-bulges, and investigate the relation between their stellar masses and central stellar velocity dispersion σ. Assuming a single relation between elliptical galaxy/bulge mass, MBulge, and central black hole mass, MBH, we find that 55 +8 −4 per cent of the mass in black holes in the local universe is in the centres of elliptical galaxies, 41 −2 per cent in classical bulges and 4 +0.9 −0.4 per cent in pseudo-bulges. We find that ellipticals, classical bulges and pseudo-bulges follow different relations between their stellar masses and σ, and the most significant offset occurs for pseudo-bulges in barred galaxies. This structural dissimilarity leads to discrepant black hole masses if single MBH − MBulge and MBH − σ relations are used. Adopting relations from the literature, we find that the MBH −σ relation yields an estimate of the total mass density in black holes that is roughly 55 per cent larger than if the MBH −MBulge relation is used.