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 \sigma .
Assuming a single relation between elliptical galaxy/bulge mass , M _ { Bulge } , and central black hole mass , M _ { BH } , 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 ^ { +4 } _ { -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 \sigma , and the most significant offset occurs for pseudo-bulges in barred galaxies .
This structural dissimilarity leads to discrepant black hole masses if single M _ { BH } - M _ { Bulge } and M _ { BH } - \sigma relations are used .
Adopting relations from the literature , we find that the M _ { BH } - \sigma relation yields an estimate of the total mass density in black holes that is roughly 55 per cent larger than if the M _ { BH } - M _ { Bulge } relation is used .