Galaxies with the spectra of giant H II regions.
Abstract
The properties and nature of 14 galaxies which exhibit strong, sharp, H II region-like emission lines are investigated. Line fluxes in the region 3700-7100 A were obtained for ten low-luminosity compact objects with absolute magnitudes greater than -17 and four with magnitudes less than -20 and used to derive electron temperatures and densities and helium, oxygen, nitrogen, neon and sulfur abundances. The galaxies are found to be almost certainly photoionized by hot main-sequence stars. Determination of the velocity dispersion for one object reveals that the mass of stars within it is several times smaller than the mass of neutral hydrogen found around it. Continuum colors of the galaxies are observed to be very blue, with no older red population apparent. Comparison of the relative abundances in these galaxies with respect to their normal values is performed in an investigation of galactic chemical evolution, and a primordial helium abundance of 0.069 is obtained. Data are shown to be consistent with young galaxies, having formed most of their stars recently, and with brief, periodic bursts of star formation in the low-luminosity objects.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1980
- DOI:
- 10.1086/158205
- Bibcode:
- 1980ApJ...240...41F
- Keywords:
-
- Abundance;
- Astronomical Spectroscopy;
- Emission Spectra;
- Galactic Evolution;
- Galactic Structure;
- H Ii Regions;
- Line Spectra;
- Chemical Evolution;
- Hot Stars;
- Luminous Intensity;
- Main Sequence Stars;
- Nuclear Fusion;
- Photoionization;
- Spectrum Analysis;
- Stellar Mass;
- Tables (Data);
- Velocity Distribution;
- Astrophysics