The estimation of black-hole masses in distant radio galaxies

We have estimated the masses of the central supermassive black holes of 2442 radio galaxies from a catalog. Mass estimates based on optical photometry and radio data are compared. Relationships between the mass of the central black hole Mbh p and the redshift zp are constructed for both wavelength ranges (radio and optic). Upper-envelope cubic regression fits are obtained using the maximum estimates of the black-hole masses. The optical and radio upper envelopes show similar behavior, and have very similar peaks in position, zp ≃ 1:9 and amplitude, log M bh p =9.4. This is consistent with a model in which the growth of the supermassive black holes is self-regulating, with this redshift corresponding to the epoch when the accretion-ow phase begins to end and the nuclear activity falls off