What distinguishes the host galaxies of radio-loud and radio-quiet AGNs?

TL;DR

This study compares host galaxy properties of radio-loud and radio-quiet AGNs, revealing differences in morphology and extinction but not in merger features, suggesting host characteristics influence jet production.

Contribution

It demonstrates that, after matching for black hole mass and Eddington ratio, host galaxy morphology and extinction differ between RL and RQ AGNs, highlighting the role of host properties in jet activity.

Findings

RL AGNs are more often in elliptical galaxies.

Galaxies with higher radio loudness have lower nebular extinction.

No significant difference in merger features between RL and RQ hosts.

Abstract

We compare the optical properties of the host galaxies of radio-quiet (RQ) and radio-loud (RL) Type 2 active galactic nuclei (AGNs) to infer whether the jet production efficiency depends on the host properties or is determined just by intrinsic properties of the accretion flows. We carefully select galaxies from SDSS, FIRST, and NVSS catalogs. We confirm previous findings that the fraction of RL AGNs depends on the black-hole (BH) masses, and on the Eddington ratio. The comparison of the nature of the hosts of RL and RQ AGNs, therefore, requires pair-matching techniques. Matching in BH mass and Eddington ratio allows us to study the differences between galaxies hosting RL and RQ AGNs that have the same basic accretion parameters. We show that these two samples differ predominantly in the host-galaxy concentration index, morphological type (in the RL sample the frequency of elliptical galaxies becoming larger with increasing radio loudness), and nebular extinction (galaxies with highest radio loudness showing only low nebular extinction). Contrary to some previous studies, we find no significant difference between our radio-loud and radio-quiet samples regarding merger/interaction features.