The Square Kilometre Array (SKA)

Abstract:

Using a Karl G. Jansky Very Large Array (VLA) L-band (1-2 GHz) survey covering∼100 deg^2 of the Stripe 82 field, we have obtained a catalogue of 2716 radio AGNs. For these AGNs, we investigate the impact of galaxy density on 1.4 GHz radio luminosity (L1.4).We determine their close environment densities using the surface density parameter, ΣN, for N = 2 and N = 5, which we bin by redshift to obtain a pseudo-3D galaxy density measure. Matching the radio AGNs to sources without radio detections in terms of redshift, K-band magnitude and (g−K) colour index, we obtain samples of control galaxies and determine whether radio AGN environments differ from this general population. Our results indicate that the environmental density of radio AGNs and their radio luminosity are not correlated up to z ∼ 0.8, over the luminosity range 10^23 < (L1.4/W Hz−1) < 10^26.We also find that, when using a control sample matched in terms of redshift, K-band magnitude and colour, environments of radio AGNs are similar to those of the control sample but with an excess of overdense regions in which radio AGNs aremore prevalent. Our results suggest that the <1Mpc-scale galaxy environment plays some role in determining whether a galaxy produces a radio AGN. The jet power, however, does not correlate with environment. From this, we infer that secular processes, e.g. accretion flows of cold gas to the central black hole are more critical in fuelling radio AGN activity than radio jet power.