The disc-dominated host galaxy of FR-I radio source B2 0722+30

TL;DR

This study reveals that B2 0722+30 is a rare disc galaxy hosting a classical double-lobed radio source, with detailed analysis of its gas, star formation, and environment, challenging typical galaxy-radio source associations.

Contribution

It provides detailed multi-wavelength observations and analysis of a rare disc galaxy hosting a classical radio-loud AGN, highlighting environmental factors influencing such systems.

Findings

B2 0722+30 is a disc galaxy with a classical double-lobed radio source.

The galaxy has a regularly rotating gaseous disc with ongoing star formation.

The environment is HI-rich with interacting galaxies, likely triggering the radio AGN.

Abstract

We present new observational results that conclude that the nearby radio galaxy B2 0722+30 is one of the very few known disc galaxies in the low-redshift Universe that host a classical double-lobed radio source. In this paper we use HI observations, deep optical imaging, stellar population synthesis modelling and emission-line diagnostics to study the host galaxy, classify the Active Galactic Nucleus and investigate environmental properties under which a radio-loud AGN can occur in this system. Typical for spiral galaxies, B2 0722+30 has a regularly rotating gaseous disc throughout which star formation occurs. Dust heating by the ongoing star formation is likely responsible for the high infrared luminosity of the system. The optical emission-line properties of the central region identify a Low Ionization Nuclear Emission-line Region (LINER)-type nucleus with a relatively low [OIII] luminosity, in particular when compared with the total power of the Fanaroff & Riley type-I radio source that is present in this system. This classifies B2 0722+30 as a classical radio galaxy rather than a typical Seyfert galaxy. The environment of B2 0722+30 is extremely HI-rich, with several nearby interacting galaxies. We argue that a gas-rich interaction involving B2 0722+30 is a likely cause for the triggering of the radio-AGN and/or the fact that the radio source managed to escape the optical boundaries of the host galaxy.