An Extended View of the Fornax Cluster

The Multibeam survey at the Parkes Radio Telescope has provided a wealth of 21-cm HI data. We have mosaicked ten standard HIPASS cubes to produce a datacube approximately 25 degrees x25 degrees in size, centred on NGC 1399, the optical centre of the Fornax Cluster. Some properties of the initial similar to 80 galaxies identified in HI are described. In the optical, Ferguson's Fornax Cluster Catalogue (FCC) (Ferguson 1989) identified 340 likely member galaxies in the central 40 deg(2). In the radio we have detected a more uniform sheet of about 80 galaxies at the cluster velocity extending up to 15 degrees from the cluster centre. At the cluster distance of about 15 Mpc, this corresponds to an elongated structure more than 7 Mpc in extent. Galaxies were detected to a lower mass limit of similar to 1 x 10(8) M-circle dot and fewer than 25 of these were within the central 40 deg(2), suggesting considerable HI depletion of galaxies in the centre of the cluster. Further, these results strongly indicate that HI surveys do not readily identify galaxy clusters.