Radio Bimodality: Spin, Accretion Mode, or Both?

TL;DR

This paper proposes a new scenario linking black hole growth, galaxy morphology, and radio properties of AGNs, emphasizing the roles of spin and accretion mode in explaining radio dichotomy.

Contribution

It introduces a model connecting black hole spin and accretion mode to AGN radio properties, explaining the observed dichotomy based on galaxy morphology.

Findings

Black hole spin is higher in giant ellipticals than in disk galaxies.

Radio dichotomy correlates with galaxy morphology and black hole spin.

A scenario for producing powerful radio sources at high accretion rates is proposed.

Abstract

A new scenario is suggested to explain a large diversity of the AGN radio properties and their dependence on the galaxy morphology. The scenario is based on the assumption that the growth of supermassive BHs is dominated by the accretion only during the quasar (high accretion rate) phase, otherwise - by mergers with less massive black holes. Following that, BHs are expected to spin much faster in giant ellipticals than in disk galaxies. Within the frame of the spin paradigm this explains the observed relation of the radio-dichotomy with the galaxy morphology. Various theoretical and observational aspects of such a dichotomy are discussed. In particular, the issue of the intermittency and suppression of a jet production at high accretion rates is addressed and a scenario for production of powerful, extended radio sources is drafted.