Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 445, Issue 1, Pages 955-969Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stu1776
Keywords
accretion, accretion discs; galaxies: active; galaxies: evolution; galaxies: jets; radio continuum: galaxies
Categories
Funding
- STFC
- NWO [NWO-TOPLOFAR614.001.006]
- [W/12A/P16]
- [W/12B/P7]
- STFC [ST/J004626/1, ST/J001465/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/J001465/1, ST/J004626/1] Funding Source: researchfish
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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 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-14 (GHz) less than or similar to 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 jetmode 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.
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