HI absorption in nearby compact radio galaxies
  HI absorption studies yield information on both AGN feeding and feedback
processes. This AGN activity interacts with the neutral gas in compact radio
sources, which are believed to represent the young or recently re-triggered AGN
population. We present the results of a survey for HI absorption in a sample of
66 compact radio sources at 0.040 < z < 0.096 with the Australia Telescope
Compact Array. In total, we obtained seven detections, five of which are new,
with a large range of peak optical depths (3% to 87%). Of the detections, 71%
exhibit asymmetric, broad ($\Delta{v}_{\mathrm{FWHM}}$ > 100 km s$^{-1}$)
features, indicative of disturbed gas kinematics. Such broad, shallow and
offset features are also found within low-excitation radio galaxies which is
attributed to disturbed circumnuclear gas, consistent with early-type galaxies
typically devoid of a gas-rich disk. Comparing mid-infrared colours of our
galaxies with HI detections indicates that narrow and deep absorption features
are preferentially found in late-type and high-excitation radio galaxies in our
sample. These features are attributed to gas in galactic disks. By combining
XMM-Newton archival data with 21-cm data, we find support that absorbed X-ray
sources may be good tracers of HI content within the host galaxy. This sample
extends previous HI surveys in compact radio galaxies to lower radio
luminosities and provides a basis for future work exploring the higher redshift
universe.
