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

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

Abstract

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 () 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 emission line ratio we could, for the first time, determine a rather reliable foreground extinction of = 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)/ 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

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations and reductions
• 3. Results and discussion
  • 3.1. Direct image
  • 3.2. Optical spectrum
  • 3.3. The nature of the nebula
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: March 23, 1998
helpdesk@link.springer.de