Mass function of active black holes

Using the ~8500 broad-line active galaxies from SDSS-DR4, we construct a broad-line luminosity function that agrees very well with the local soft X-ray luminosity function. Using standard virial relations, we then convert observed broad-line luminosities and widths into BH masses.

A mass function constructed in this way has the unique capability to probe the mass region <10^6^M_{sun}_ which, while insignificant in terms of total BH mass density, nevertheless may place important constraints on the mass distribution of seed BHs in the early universe.