The prevalence of AGN feedback in massive galaxies at z~1

TL;DR

This study investigates the prevalence of AGN feedback in massive galaxies at around redshift 1 by analyzing radio luminosity distributions and their relation to star formation activity, suggesting a long-standing energy balance mechanism.

Contribution

It introduces a new Bayesian classification method for galaxies and demonstrates that the energy balance between AGN heating and gas cooling was already in place at z~1.

Findings

Radio luminosity distribution matches local universe for weak-lined radio galaxies

Evidence of a long-standing energy balance between AGN heating and gas cooling at z~1

Low-luminosity radio-loud AGNs are linked to suppressed star formation

Abstract

We use the optical--infrared imaging in the UKIDSS Ultra Deep Survey field, in combination with the new deep radio map of Arumugam et al., to calculate the distribution of radio luminosities among galaxies as a function of stellar mass in two redshift bins across the interval 0.4<z<1.2. This is done with the use of a new Bayesian method to classify stars and galaxies in surveys with multi-band photometry, and to derive photometric redshifts and stellar masses for those galaxies. We compare the distribution to that observed locally and find agreement if we consider only objects believed to be weak-lined radio-loud galaxies. Since the local distribution is believed to be the result of an energy balance between radiative cooling of the gaseous halo and mechanical AGN heating, we infer that this balance was also present as long ago as z~1. This supports the existence of a direct link between the presence of a low-luminosity ('hot-mode') radio-loud active galactic nucleus and the absence of ongoing star formation.