The link between accretion mode and environment in radio-loud active
  galaxies
  The interactions between radio-loud AGN and their environments play an
important role in galaxy and cluster evolution. Recent work has demonstrated
fundamental differences between High and Low Excitation Radio Galaxies (HERGs
and LERGs), and shown that they may have different relationships with their
environments. In the Chandra Large Project ERA (Environments of Radio-loud
AGN), we made the first systematic X-ray environmental study of the cluster
environments of radio galaxies at a single epoch (z~0.5), and found tentative
evidence for a correlation between radio luminosity and cluster X-ray
luminosity. We also found that this relationship appeared to be driven by the
LERG sub-population (Ineson et al. 2013).
  We have now repeated the analysis with a low redshift sample (z~0.1), and
found strong correlations between radio luminosity and environment richness and
between radio luminosity and central density for the LERGs but not for the
HERGs. These results are consistent with models in which the HERGs are fuelled
from accretion discs maintained from local reservoirs of gas, while LERGs are
fuelled more directly by gas ingested from the intra-cluster medium.
  Comparing the samples, we found that although the maximum environment
richness of the HERG environments is similar in both samples, there are poorer
HERG environments in the z~0.1 sample than in the z~0.5 sample. We have
therefore tentative evidence of evolution of the HERG environments. We found no
differences between the LERG sub-samples for the two epochs, as would be
expected if radio and cluster luminosity are related.
