A bright emission region in the new nearby dwarf irregular galaxy Cassiopeia 1
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 Hii regions, one of these objects (l =3D 129fdg6 , b =3D +7fdg1 ) was suspected to be a dwarf irregular galaxy, named Cas 1. We have obtained optical spectra of the brightest Hii candidate in Cas 1. By using the H_alpha /H_beta emission line ratio we could, for the first time, determine a rather reliable foreground extinction of A_V =3D 2.5 mag and thus cannot support Tikhonov's (1996) view that Cas 1 is a member of the Local Group. For [Oiii](5007 Angstroms)/H_beta we obtained a ratio of 2.6, much higher than typical ratios for (galactic) Hii 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 Hii region, possibly excited by a WR star.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 1998
- Bibcode:
- 1998A&A...332..523W
- Keywords:
-
- GALAXIES: INDIVIDUAL CAS 1;
- GALAXIES: IRREGULAR;
- GALAXIES: ISM;
- GALAXIES: DWARF