Unification of Radio Galaxies and Their Accretion/Jet Properties

TL;DR

This study explores the relationship between black hole mass, jet power, and accretion modes in radio galaxies, supporting the unification scheme of different galaxy types and suggesting rapidly spinning black holes.

Contribution

It provides evidence linking black hole properties with galaxy classifications and proposes a model involving high black hole spin to explain observed jet and accretion features.

Findings

BL Lacs and radio quasars are separated by the FR I/II dividing line in M_bh-Q_jet plane.

Eddington ratio distribution is bimodal with a division at ~0.01.

Black holes in radio galaxies are likely rapidly spinning.

Abstract

We investigate the relation between black hole mass, M_bh, and jet power, Q_jet, for a sample of BL Lacs and radio quasars. We find that BL Lacs are separated from radio quasars by the FR I/II dividing line in M_bh-Q_jet plane, which strongly supports the unification scheme of FR I/BL Lac and FR II/radio quasar. The Eddington ratio distribution of BL Lacs and radio quasars exhibits a bimodal nature with a rough division at L_bol/L_Edd~0.01, which imply that they may have different accretion modes. We calculate the jet power extracted from advection dominated accretion flow (ADAF), and find that it require dimensionless angular momentum of black hole j~0.9-0.99 to reproduce the dividing line between FR I/II or BL Lac/radio quasar if dimensionless accretion rate mdot=0.01 is adopted, which is required by above bimodal distribution of Eddington ratios. Our results suggest that black holes in radio galaxies are rapidly spinning.