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Astron. Astrophys. 332, 523-525 (1998)

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Research Note

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

R. Weinberger and W. Saurer

Institut für Astronomie der Leopold-Franzens-Universität, Technikerstraße 25, A-6020 Innsbruck, Austria

Received 28 April 1997 / Accepted 9 December 1997


In recent years several dwarf galaxies belonging to the highly obscured Maffei-IC 342 group have been discovered. Due to its shape, colour and the presence of a few possible H II regions, one of these objects ([FORMULA]) 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 [FORMULA] emission line ratio we could, for the first time, determine a rather reliable foreground extinction of [FORMULA] = 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)/ [FORMULA] we obtained 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.

Key words: galaxies: individual Cas 1 – galaxies: irregular – galaxies: ISM – galaxies: dwarf

Send offprint requests to: R. Weinberger

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© European Southern Observatory (ESO) 1998

Online publication: March 23, 1998