A search for HI absorption in nearby radio galaxies using HIPASS
  Using archival data from the HI Parkes All Sky Survey (HIPASS) we have
searched for 21 cm line absorption in 204 nearby radio and star-forming
galaxies with continuum flux densities greater than $S_{1.4} \approx 250$ mJy
within the redshift range $0 < cz < 12000$ km s$^{-1}$. By applying a detection
method based on Bayesian model comparison, we successfully detect and model
absorption against the radio-loud nuclei of four galaxies, of which the Seyfert
2 galaxy 2MASX J130804201-2422581 was previously unknown. All four detections
were achieved against compact radio sources, which include three active
galactic nuclei (AGNs) and a nuclear starburst, exhibiting high dust and
molecular gas content. Our results are consistent with the detection rate
achieved by the recent ALFALFA (Arecibo Legacy Fast Arecibo L-band Feed Array)
HI absorption pilot survey by Darling et al. and we predict that the full
ALFALFA survey should yield more than three to four times as many detections as
we have achieved here. Furthermore, we predict that future all-sky surveys on
the Square Kilometre Array precursor telescopes will be able to detect such
strong absorption systems associated with type 2 AGNs at much higher redshifts,
providing potential targets for detection of H$_{2}$O megamaser emission at
cosmological redshifts.
