A bright emission region in the new nearby dwarf irregular galaxy Cassiopeia 1

In recent years several dwarf galaxies belonging to the highly obscuredMaffei–IC 342grouphave been discovered. Due to its shape, colour and the presence of a few possible H ii regions, one of these objects (` = 129. ◦6, b = +7. ◦1) was suspected to be a dwarf irregular galaxy, named Cas 1. We have obtained optical spectra of the brightest H ii candidate in Cas 1. By using the Hα/Hβ emission line ratio we could, for the first time, determine a rather reliable foreground extinction of AV = 2.5 mag and thus cannot support Tikhonov’s (1996) view that Cas 1 is a member of the Local Group. For [O iii](5007 Å)/Hβ weobtained a ratio of 2.6,much higher than typical ratios for (galactic) H ii regions. The nature of the emitting nebula is unclear: a supernova remnant seems to be implausible (there is an IRAS counterpart), but we might deal with an H ii region, possibly excited by a WR star.