FCC 35 and Its H I Companion: Multiwavelength Observations and Interpretation

The Fornax Cluster galaxy FCC 35 shows an unusual multiply peaked integrated H I profile. We have now observed FCC 35 with the Australia Telescope Compact Array and have found a compact H I source with MHI = 2.2 × 108 M☉ and a spatially overlapping complex of H I gas with the same mass. By combining optical observations with the H I data, we are able to identify FCC 35 as a young compact source of star formation with a nearby intergalactic H I cloud that is devoid of stars. We classify FCC 35 as a blue compact dwarf or H II 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 H I cloud, this suggests that FCC 35 is the result of a recent interaction within the Fornax Cluster.