The mass function of nearby black holes

Here we use this catalogue to derive the black-hole mass function. We also correct for volume, so that this mass function is a volume-limited distribution to redshift 0.025. The differential mass function of nearby black hole candidates is a curved function, with a straight simple power-law of index -3 above 10^8^M_{sun}_ that becomes progressively flatter towards lower masses, turns off towards a gap below 3x10^6^M_{sun}_, and then extends into the range where nuclear star clusters replace black holes.

The shape of this mass function can be explained in a simple merger picture. Integrating this mass function over the redshift range for which it has been derived, infers a total number of black holes with z<0.025, and M_BH_>10^7^M_{sun}_ of about 2.4x10^4^, or, if we average uniformly, 0.6 for every square degree on the sky.