paper

Galaxy And Mass Assembly (GAMA): The environments of high- and low- excitation radio galaxies

arXiv:1705.04502 · doi:10.1093/mnras/stx1173

Abstract

We study the environments of low- and high- excitation radio galaxies (LERGs and HERGs respectively) in the redshift range , using a sample of 399 radio galaxies and environmental measurements from the Galaxy And Mass Assembly (GAMA) survey. In our analysis we use the fifth nearest neighbour density () and the GAMA galaxy groups catalogue (G3Cv6) and construct control samples of galaxies matched in {\update stellar mass and colour} to the radio-detected sample. We find that LERGs and HERGs exist in different environments and that this difference is dependent on radio luminosity. High-luminosity LERGs ( W Hz) lie in much denser environments than a matched radio-quiet control sample (about three times as dense, as measured by ), and are more likely to be members of galaxy groups ( percent of LERGs are in GAMA groups, compared to percent of the control sample). In contrast, the environments of the HERGs and lower luminosity LERGs are indistinguishable from that of a matched control sample. Our results imply that high-luminosity LERGs lie in more massive haloes than non-radio galaxies of similar stellar mass and colour, in agreement with earlier studies (Wake et al. 2008; Donoso et al. 2010). When we control for the preference of LERGs to be found in groups, both high- and low- luminosity LERGs are found in higher-mass haloes ( dex; at least 97 percent significant) than the non-radio control sample.

arXiv comment18 pages, 11 figures. Accepted for publication by MNRAS

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