H [CSC]i[/CSC] in Four Star-forming Low-Luminosity E/S0 and S0 Galaxies

We present HI data cubes of four low-luminosity early-type galaxies which arecurrently forming stars. These galaxies have absolute magnitudes in the rangeM_B=-17.9 to -19.9 (H_o=50 km/s/Mpc). Their HI masses range between a few times10^8 and a few times 10^9 M_sun and the corresponding values for M_HI/L_B arebetween 0.07 and 0.42, so these systems are HI rich for their morphologicaltype. In all four galaxies, the HI is strongly centrally concentrated with highcentral HI surface densities, in contrast to what is typically observed in moreluminous early-type galaxies. In two galaxies (NGC 802 and ESO 118-G34), thekinematics of the HI suggests that the gas is in a strongly warped disk, whichwe take as evidence for recent accretion of HI. In the other two galaxies (NGC2328 and ESO 027-G21) the HI must have been part of the systems for aconsiderable time. The HI properties of low-luminosity early-type galaxiesappear to be systematically different from those of many more luminousearly-type galaxies, and we suggest that these differences are due to adifferent evolution of the two classes. The star formation history of thesegalaxies remains unclear. Their UBV colours and Halpha emission-line strengthsare consistent with having formed stars at a slowly-declining rate for most ofthe past 10^10 years. However, the current data do not rule out a small burstof recent star formation overlaid on an older stellar population.