2005MNRAS.360..853B

We present Hi 21-cm line observations, obtained with the Australia Telescope Compact Array, of two dwarf elliptical galaxies (dEs) in the Fornax cluster: FCC032 and FCC336. The optical positions and velocities of these galaxies place them well within the Fornax cluster. FCC032 was detected at the 3σ significance level with a total Hi flux density of 0.66±0.22 Jy.km/s or an Hi mass of 5.0±1.7x10⁷h^–2₇₅M_☉. Based on our deep Hα+[Nii] narrow-band images, obtained with FORS2 mounted on the Very Large Telescope, this dE was already known to contain 600 -1800h^–2₇₅M_☉of ionized hydrogen (depending on the relative strengths of the Hα and [Nii] emission lines). Hence, this is the first study of the complex, multiphase interstellar medium of a dE outside the Local Group. FCC336 was detected at the same significance level: 0.37±0.10 Jy km/s or a total Hi mass of 2.8±0.7x10⁷h^–2₇₅M_☉. Using a compilation of Hi data of dwarf galaxies, we find that the observed high Hi mass boundary of the distribution of dwarf irregulars, blue compact dwarfs and dwarf ellipticals in a logL_B versus logM_Hidiagram is in good agreement with a simple chemical evolution model with continuous star formation. The existence of many gas-poor dEs (undetected at 21 cm) suggests that the environment (or, more particularly, a galaxy's orbit within a cluster) also plays a crucial role in determining the amount of gas in present-day dEs; for example, FCC032 and FCC336 are located in the sparsely populated outskirts of the Fornax cluster. This is in agreement with Hi surveys of dEs in the Virgo cluster, and an Hα survey of the Fornax cluster, which also tend to place gas-rich dwarf galaxies in the cluster periphery.