| Abstract | The results of 21-cm neutral hydrogen survey observations, made using the 64-m Parkes telescope, are presented for two 8 deg by 8 deg fields, centred on the Centaurus and Fornax galaxy clusters, and a smaller 1 deg.5 field in Eridanus. The purpose of the observations was to search for extended Hi clouds with no clear optical counterparts. 31 previously catalogued galaxies were detected, with Hi parameters for 16 being listed for the first time. One previously uncatalogued dwarf galaxy (`Wombat I', J0341-3851) was found near the Fornax cluster. Australia Telescope Compact Array observations give an Hi mass of 8x10^7 Msolar and a diameter of 4kpc for this object, which is also visible on UKST survey plates. However, no clouds with optically invisible counterparts were detected. We deduce a 99 per cent confidence limit on the total Hi density of such objects in the cluster and near-cluster environment of Omega_HI<10^-2h^-1(deltaV/100kms^-1. |
