Metal Abundances of KISS Galaxies. III. Nebular Abundances for Fourteen Galaxies and the Luminosity-Metallicity Relationship for H II Galaxies
Abstract
We report results from the third in a series of nebular abundance studies of emission-line galaxies from the KPNO International Spectroscopic Survey (KISS). Galaxies with coarse metallicity estimates of 12+log(O/H) less than 8.2 dex were selected for observation. Spectra of 14 galaxies, which cover the full optical region from [O II] λλ3727, 3729 to beyond [S II] λλ6717, 6731, are presented, and abundance ratios of N, O, Ne, S, and Ar are computed. The auroral [O III] λ4363 line is detected in all 14 galaxies. Oxygen abundances determined through the direct electron temperature (Te) method confirm that the sample is metal-poor with 7.61<=12+log(O/H)<=8.32. By using these abundances in conjunction with other Te-based measurements from the literature, we demonstrate that H II galaxies and more quiescent dwarf irregular galaxies follow similar metallicity-luminosity (L-Z) relationships. The primary difference is a zero-point shift between the correlations such that H II galaxies are brighter by an average of 0.8 B magnitudes at a given metallicity. This offset can be used as evidence to argue that low-luminosity H II galaxies typically undergo factor of 2 luminosity enhancements, and starbursts that elevate the luminosities of their host galaxies by 2-3 mag are not as common. We also demonstrate that the inclusion of interacting galaxies can increase the scatter in the L-Z relation and may force the observed correlation toward lower metallicities and/or larger luminosities. This must be taken into account when attempting to infer metal abundance evolution by comparing local L-Z relations with ones based on higher redshift samples, since the fraction of interacting galaxies should increase with look-back time.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2004
- DOI:
- 10.1086/425156
- arXiv:
- arXiv:astro-ph/0408342
- Bibcode:
- 2004ApJ...616..752L
- Keywords:
-
- Galaxies: Abundances;
- Galaxies: Dwarf;
- Galaxies: Evolution;
- Galaxies: Starburst;
- ISM: H II Regions;
- Astrophysics
- E-Print:
- 36 pages, 5 figures. ApJ, in press