Radio-mode feedback in local AGNs: dependence on the central black hole parameters

TL;DR

This study investigates how radio-mode feedback in local AGNs correlates with central black hole properties, revealing that more massive black holes with low accretion rates are more likely to produce radio jets, supporting a two-stage feedback model.

Contribution

It provides new observational evidence linking black hole mass and accretion rate to radio jet activity in local AGNs, emphasizing the role of radiatively inefficient accretion in feedback.

Findings

Radio galaxies are associated with more massive black holes.

Radio loudness increases as Eddington ratio decreases.

Most local radio galaxies are in a radiatively inefficient accretion regime.

Abstract

Radio mode feedback, in which most of the energy of an active galactic nucleus (AGN) is released in a kinetic form via radio-emitting jets, is thought to play an important role in the maintenance of massive galaxies in the present-day Universe. We study the link between radio emission and the properties of the central black hole in a large sample of local radio galaxies drawn from the Sloan Digital Sky Survey (SDSS), based on the catalogue of Best and Heckman (2012). Our sample is mainly dominated by massive black holes (mostly in the range $10^8-10^9 M_{\odot}$) accreting at very low Eddington ratios (typically $\lambda < 0.01$). In broad agreement with previously reported trends, we find that radio galaxies are preferentially associated with the more massive black holes, and that the radio loudness parameter seems to increase with decreasing Eddington ratio. We compare our results with previous studies in the literature, noting potential biases. The majority of the local radio galaxies in our sample are currently in a radiatively inefficient accretion regime, where kinetic feedback dominates over radiative feedback. We discuss possible physical interpretations of the observed trends in the context of a two-stage feedback process involving a transition in the underlying accretion modes.