Blazars in the early Universe

Understand

We investigate the relative occurrence of radio--loud and radio-quiet quasars in the first billion years of the Universe, powered by black holes heavier than one billion solar masses.

• We consider the sample of high-redshfit blazars detected in the hard X-ray band in the 3-years all sky survey performed by the Burst Alert Telescope (BAT) onboard the Swift satellite.
• All the black holes powering these blazars exceed a billion solar mass, with accretion luminosities close to the Eddington limit.
• For each blazar pointing at us, there must be hundreds of similar sources (having black holes of similar masses) pointing elsewhere.