| Authors | Waugh, Meryl; Drinkwater, M. J.; Webster, R. L.; Staveley-Smith, L.; Kilborn, V. A.; Barnes, D. G.; Bhathal, R.; de Blok, W. J. G.; Boyce, P. J.; Disney, M. J.; Ekers, R. D.; Freeman, K. C.; Gibson, B. K.; Henning, P. A.; Jerjen, H.; Knezek, P. M.; Koribalski, B.; Marquarding, M.; Minchin, R. F.; Price, R. M.; Putman, M. E.; Ryder, S. D.; Sadler, E. M.; Stootman, F.; Zwaan, M. A. |
| Abstract | Using data from the HI Parkes All Sky Survey (HIPASS), we have searched for neutral hydrogen in galaxies in a region ~25 × 25 deg2 centred on NGC 1399, the nominal centre of the Fornax cluster. Within a velocity search range of 300-3700 km s-1 and to a 3σ lower flux limit of ~40 mJy, 110 galaxies with HI emission were detected, one of which is previously uncatalogued. None of the detections has early-type morphology. Previously unknown velocities for 14 galaxies have been determined, with a further four velocity measurements being significantly dissimilar to published values. Identification of an optical counterpart is relatively unambiguous for more than ~90 per cent of our HI galaxies. The galaxies appear to be embedded in a sheet at the cluster velocity which extends for more than 30° across the search area. At the nominal cluster distance of ~20 Mpc, this corresponds to an elongated structure more than 10 Mpc in extent. A velocity gradient across the structure is detected, with radial velocities increasing by ~500 km s-1 from south-east to north-west. The clustering of galaxies evident in optical surveys is only weakly suggested in the spatial distribution of our HI detections. Of 62 HI detections within a 10° projected radius of the cluster centre, only two are within the core region (projected radius <1°) and less than 30 per cent are within 3.5°, suggesting a considerable deficit of HI-rich galaxies in the centre of the cluster. However, relative to the field, there is a 3(+/-1)-fold excess of HI-rich galaxies in the outer parts of the cluster where galaxies may be infalling towards the cluster for the first time. |
