The Discovery of the Smallest Blue Compact Dwarf Galaxies

Abstract

In a spectroscopic survey of the Fornax cluster to Bj=17.5 using the FLAIR spectrograph on the UK Schmidt Telescope we have discovered seven new compact dwarf cluster members. These were previously thought to be giant background spirals. These new members are among the most compact, high surface brightness dwarf galaxies known with absolute magnitudes of M_B=-14 and scale lengths of alpha=400 pc. One in particular may be the first high (normal) surface brightness dwarf spiral discovered. Three of the new dwarfs are blue compact dwarfs (BCDs); their inclusion in the cluster increases the faint end of the BCD luminosity function by a factor of 2 or more. We extended the survey 2.5 mag fainter with the 2dF spectrograph and in our first field found 7 bright emission line galaxies beyond the Fornax cluster which were unresolved on the sky survey plates. Galaxies of this type would be missed in most existing galaxy surveys.