Detection of Neutral Hydrogen in Early-Type Dwarf Galaxies of the Sculptor Group

We present our results of deep 21 cm line (HI) observations of five early andmixed-type dwarf galaxies in the nearby Sculptor group using the ATNF 64mParkes Radio Telescope. Four of these objects, ESO294-G010, ESO410-G005,ESO540-G030, and ESO540-G032, were detected in HI with neutral hydrogen massesin the range of 2-9x10^5 M_{\odot} ($M_{HI}/L_{B}$ = 0.08, 0.13, 0.16, and0.18, respectively). These HI masses are consistent with the gas mass expectedfrom stellar outflows over a large period of time. Higher resolution radio datafrom the Australia Telescope Compact Array were further analysed to measuremore accurate positions and the distribution of the HI gas. In the cases ofdwarfs ESO294-G010 and ESO540-G030, we find significant offsets of 290 pc and460 pc, respectively, between the position of the HI peak flux and the centerof the stellar component. These offsets are likely to have internal cause suchas the winds from star-forming regions. The fifth object, the spatiallyisolated dwarf elliptical Scl-dE1, remains undetected at our 3\sigma limit of22.5 mJy km/s and thus must contain less than 10^5 M_{\odot} of neutralhydrogen. This leaves Scl-dE1 as the only Sculptor group galaxy known where nointerstellar medium has been found to date. The object joins a list of similarsystems including the Local Group dwarfs Tucana and Cetus that do not fit intothe global picture of the morphology-density relation where gas-rich dwarfirregulars are in relative isolation and gas-deficient dwarf ellipticals aresatellites of more luminous galaxies.Comment: 21 pages, 4 figures, to be published in AJ (accepted