Detection of neutral hydrogen in early-type Dwarf galaxies of the sculptor group

We present results of deep 21 cm neutral hydrogen (Hi) line observations of five early- and mixed-type dwarf galaxies in the nearby Sculptor group using the Australia Telescope National Facility 64 m Parkes Radio Telescope. Four of these objects, ESO 294-G010, 410-G005, 540-G030, and 540-G032, were detected in H I with neutral hydrogen masses in the range (2-9) × 10⁵ M^⊙ (M_{H I}/L_B = 0.08, 0.13, 0.16, and 0.18 M _⊙ respectively). These H I masses are consistent with the gas mass expected from stellar outflows over a large period of time. Higher spatial resolution H I data from the Australia Telescope Compact Array interferometer were further analyzed to measure more accurate positions and the distribution of the H I gas. In the cases of the dwarfs ESO 294-G010 and ESO 540-G030, we find significant offsets of 290 and 460 pc, respectively, between the position of the H I peak flux and the center of the stellar component. These offsets are likely to have internal causes such as the winds from star-forming regions. The fifth object, the spatially isolated dwarf elliptical galaxy Scl-dEl, remains undetected at our 3 σ limit of 22.5 mJy km s^-1 and thus must contain less than 10⁵ M_⊙ of neutral hydrogen. This leaves Scl-dEl as the only Sculptor group galaxy known in which no interstellar medium has been found to date. The object joins a list of similar systems, including the Local Group dwarfs Tucana and Cetus, that do not fit into the global picture of the morphology-density relation in which gas-rich dwarf irregular galaxies are in relative isolation and gas-deficient dwarf elliptical galaxies are satellites of more luminous galaxies.