Virial factor of SDSS DR5 QSOs

Under the hypothesis of gravitational redshift induced by a central supermassive black hole, and based on line widths and shifts of redward-shifted H{beta} and FeII broad emission lines for a sample of 1973 z<0.8 Sloan Digital Sky Survey DR5 quasars, we measured the virial factor in determining supermassive black hole masses, usually estimated by the reverberation mapping method or the relevant secondary methods. The virial factor had been believed to be from the geometric effect of the broad-line region.

The measured virial factor of FeII is larger than that of H{beta} for 98% of these quasars. The virial factor is very different from object to object and for different emission lines. For most of these quasars, the virial factor of H{beta} is larger than these averages that were usually used in determining the masses of black holes.