Herschel-ATLAS: far-infrared properties of radio-selected galaxies

TL;DR

This study uses Herschel-ATLAS data to analyze the star-formation properties of radio-selected galaxies, finding no significant difference between radio-loud and radio-quiet galaxies in their far-infrared emission across various luminosities.

Contribution

It provides the first statistical comparison of far-infrared properties of radio-selected galaxies with matched radio-quiet counterparts, testing models of AGN triggering by mergers.

Findings

Radio-selected starburst galaxies dominate at low luminosities.

Radio-loud AGN hosts show similar far-infrared properties to radio-quiet galaxies.

No luminosity-dependent difference in star-formation activity was observed.

Abstract

We use the Herschel-ATLAS science demonstration data to investigate the star-formation properties of radio-selected galaxies in the GAMA-9h field as a function of radio luminosity and redshift. Radio selection at the lowest radio luminosities, as expected, selects mostly starburst galaxies. At higher radio luminosities, where the population is dominated by AGN, we find that some individual objects are associated with high far-infrared luminosities. However, the far-infrared properties of the radio-loud population are statistically indistinguishable from those of a comparison population of radio-quiet galaxies matched in redshift and K-band absolute magnitude. There is thus no evidence that the host galaxies of these largely low-luminosity (Fanaroff-Riley class I), and presumably low-excitation, AGN, as a population, have particularly unusual star-formation histories. Models in which the AGN activity in higher-luminosity, high-excitation radio galaxies is triggered by major mergers would predict a luminosity-dependent effect that is not seen in our data (which only span a limited range in radio luminosity) but which may well be detectable with the full Herschel-ATLAS dataset.