Gas and stellar metallicities in H ii galaxies
Article first published online: 9 FEB 2012
© 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS
Monthly Notices of the Royal Astronomical Society
Volume 421, Issue 1, pages 398–407, March 2012
How to Cite
Westera, P., Cuisinier, F., Curty, D. and Buser, R. (2012), Gas and stellar metallicities in H ii galaxies. Monthly Notices of the Royal Astronomical Society, 421: 398–407. doi: 10.1111/j.1365-2966.2012.20314.x
- Issue published online: 6 MAR 2012
- Article first published online: 9 FEB 2012
- Accepted 2011 December 1. Received 2011 November 26; in original form 2011 March 29
- ISM: abundances;
- galaxies: abundances;
- galaxies: evolution;
- galaxies: starburst
We examine the gas and stellar metallicities in a sample of H ii galaxies from the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of H ii galaxy spectra to date.
We eliminated all spectra with an insufficient signal-to-noise ratio, without strong emission lines and without the [O ii] λ3727 Å line, which is necessary for the determination of the gas metallicity. This excludes galaxies with redshift ≲ 0.033. Our final sample contains ∼700 spectra of H ii galaxies.
Through emission line strength calibrations and a detailed stellar population analysis employing evolutionary stellar synthesis methods, which we already used in previous works, we determined the metallicities of both the gas and the stellar content of these galaxies.
We find that in H ii galaxies up to stellar masses of 5 × 109 M⊙, enrichment mechanisms do not vary with galactic mass, being the same for low- and high-mass galaxies on average. They do seem to present a greater variety at the high-mass end, though, indicating a more complex assembly history for high-mass galaxies. In around 23 per cent of our H ii galaxies, we find a metallicity decrease over the last few Gyr. Our results favour galaxy evolution models featuring constantly infalling low-metallicity clouds that retain part of the galactic winds. Above 5 × 109 M⊙ stellar mass, the retention of high-metallicity gas by the galaxies’ gravitational potential dominates.