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Sjoert van Velzen (Radboud): Spin and number density of radio-loud supermassive black holes at z~1

Seminar: RAL Seminars | June 12 | 12:10-1 p.m. | B1 Hearst Field Annex

Sjoert van Velzen, Radboud Universiteit Nijmegen

Radio Astronomy Lab

FRII radio galaxies (eg, Cygnus A) can be used as a tracer of black hole activity through cosmic history as they are easy to identify in any radio survey with sufficient angular resolution. We use the FIRST survey (1.4 GHz) to obtain a homogeneous sample of hundred thousand FRIIs at z~1. Using SDSS quasars in addition, a tight correlation between disk power and lobe radio luminosity is observed. If the jet power is coupled to the black hole spin, as predicted by the Blandford-Znajek mechanism, the disk-lobe correlation implies an extremely small dispersion for the spin parameter of radio-loud quasars. We argue that this scenario could be difficult to reconcile with black hole spin evolution via merger-driven accretion. Interestingly, we measure a significant over-density of FRIIs, compared to what is expected from X-ray, optical, and near-IR quasar surveys. These diskless jets can be explained by multiple episodes of accretion over the lifetime of the radio lobes.