The relation between broad lines and gamma--ray luminosities in Fermi blazars

摘要

We study the relation between the mass accretion rate, the jet power, and theblack hole mass of blazars. To this aim, we make use of the Sloan Digital SkySurvey (SDSS) and the 11 months catalog of blazars detected at energies largerthan 100 MeV by the Large Area Telescope (LAT) onboard the Fermi satellite.This allows to construct a relatively large sample of blazars with informationabout the luminosity (or upper limits) of their emission lines used as a proxyfor the strength of the disc luminosity and on the luminosity of the highenergy emission, used as a proxy for the jet power. We find a good correlationbetween the luminosity of the broad lines and the gamma-ray luminosity asdetected by Fermi, both using absolute values of the luminosities andnormalising them to the Eddington value. The data we have analyzed confirm thatthe division of blazars into BL Lacs and Flat Spectrum Radio Quasars (FSRQs) iscontrolled by the line luminosity in Eddington units. For small values of thisratio the object is a BL Lac, while it is a FSRQs for large values. Thetransition appears smooth, but a much larger number of objects is needed toconfirm this point.