Imaging and Spectroscopy of Ionized Shells in M33 and M31
Abstract
This paper extends an examination of the spectral signature of the interaction of massive stars with the surrounding interstellar medium to the nearby spiral galaxies M33 and M31. Hα images and low- dispersion spectra have been obtained for eight giant ionized shell structures in M33 and two in M31. These structures are believed to be the result of the encircled groups of stars blowing holes in the gas through winds and supernova explosions. The emission-line ratios are compared to those of giant and supergiant shells in the LMC. Generally, the shells in M33 and M31 follow the same trend lines outlined by the shells and H II regions in the LMC with the M31 shells being offset to higher metallicity. However, unlike shells in the LMC, the M33 shells have some emission-line ratios that are not particularly distinct from those of H II regions in the same galaxy. Nevertheless, like the shells in the LMC, the emission-line ratios imply that the emission from the shells in M33 and M31 is dominated by photoionization processes. Upper limits to [O I]/Hα are consistent with this in most cases.
- Publication:
-
The Astronomical Journal
- Pub Date:
- November 1994
- DOI:
- 10.1086/117187
- Bibcode:
- 1994AJ....108.1658H
- Keywords:
-
- Astronomical Spectroscopy;
- H Alpha Line;
- H Ii Regions;
- Interstellar Matter;
- Light (Visible Radiation);
- Magellanic Clouds;
- Massive Stars;
- Spectral Signatures;
- Spiral Galaxies;
- Ultraviolet Astronomy;
- Ultraviolet Spectra;
- Visible Spectrum;
- Astronomical Photometry;
- Emission Spectra;
- Spectrographs;
- Stellar Winds;
- Astronomy;
- GALAXIES: INDIVIDUAL: M33;
- GALAXIES: INDIVIDUAL: M31;
- GALAXIES: ISM;
- GALAXIES: ABUNDANCES