FCC 35 and its HI Companion: Multi-Wavelength Observations and Interpretation

Abstract

The Fornax cluster galaxy FCC 35 shows an unusual multiply-peaked integrated HI profile (Bureau, Mould & Staveley-Smith 1996). We have now observed FCC 35 with the Australia Telescope Compact Array (ATCA) and have found a compact HI source with M_{HI} = 2.2 x 10^{8} M_{sun}, and a spatially overlapping complex of HI gas with the same mass. By combining optical observations with the HI data, we are able to identify FCC 35 as a young compact source of star formation with a nearby intergalactic HI cloud which is devoid of stars. We classify FCC 35 as a blue compact dwarf (BCD) or HII galaxy, having large amounts of neutral hydrogen, very blue colors ((U-V) = 0.1), and a low metallicity spectrum with strong narrow emission lines. Together with the presence of the HI cloud, this suggests that FCC 35 is the result of a recent interaction within the Fornax cluster.