This paper presents the first measurement of the radio luminosity function of ‘ jet-mode ’ ( radiatively-inefficient ) radio-AGN out to z = 1 , in order to investigate the cosmic evolution of radio-AGN feedback .
Eight radio source samples are combined to produce a catalogue of 211 radio-loud AGN with 0.5 < z < 1.0 , which are spectroscopically classified into jet-mode and radiative-mode ( radiatively-efficient ) AGN classes .
Comparing with large samples of local radio-AGN from the Sloan Digital Sky Survey , the cosmic evolution of the radio luminosity function of each radio-AGN class is independently derived .
Radiative-mode radio-AGN show an order of magnitude increase in space density out to z \approx 1 at all luminosities , consistent with these AGN being fuelled by cold gas .
In contrast , the space density of jet-mode radio-AGN decreases with increasing redshift at low radio luminosities ( L _ { 1.4 GHz } \mathrel { \hbox to 0.0 pt { \lower 3.0 pt \hbox { $ \mathchar 536 $ } \hss } % \raise 2.0 pt \hbox { $ \mathchar 316 $ } } 10 ^ { 24 } W Hz ^ { -1 } ) but increases at higher radio luminosities .
Simple models are developed to explain the observed evolution .
In the best-fitting models , the characteristic space density of jet-mode AGN declines with redshift in accordance with the declining space density of massive quiescent galaxies , which fuel them via cooling of gas in their hot haloes .
A time delay of 1.5–2 Gyr may be present between the quenching of star formation and the onset of jet-mode radio-AGN activity .
The behaviour at higher radio luminosities can be explained either by an increasing characteristic luminosity of jet-mode radio-AGN activity with redshift ( roughly as ( 1 + z ) ^ { 3 } ) or if the jet-mode radio-AGN population also includes some contribution of cold-gas-fuelled sources seen at a time when their accretion rate was low .
Higher redshifts measurements would distinguish between these possibilities .