A DEEP CCD SEARCH FOR LOW SURFACE BRIGHTNESS GALAXIES IN A3574

We have used the large-format Thomson CCD, operating at f/1 on the AAT, to survey a significant area (congruent-to 0.5 square degrees) of the cluster A3574 (=Shapley 1346 - 30). Detailed attention to the problem of flat-fielding the data allows us to set an extremely low detection threshold, or limiting isophote, corresponding to 26.7 Vmu or about 0.7 per cent of sky, even for objects as small as 4 arcsec2. The faintest detectable objects thus have isophotal magnitudes V congruent-to 25. We have selected out candidate cluster low surface brightness galaxies in terms of their position in an isophotal magnitude-isophotal area plot, and find 300 candidates with exponential scale-sizes greater than 2 arcsec (0.4 h-1 kpc at the cluster). The largest objects have scale-sizes 12-14 arcsec, which correspond to about 3 h-1 kpc if they are genuine cluster members, making them substantially larger than any detected in our previous surveys of Fornax and A1367, while the lowest surface brightness objects found have central values around 26.5 Vmu, slightly fainter than previously achieved. We present a catalogue of the 300 candidate objects and compare the LSBG population of this cluster with those previously surveyed. A3574 turns out to have a particularly large LSBG content, both in terms of the surface density of LSBGs and the LSBG-to-giant-galaxy ratio. We speculate that this may be due to the spiral-rich nature of the cluster.