Journal Article

Gas and stellar metallicities in H <span class="smallCaps">ii</span> galaxies

P. Westera, F. Cuisinier, D. Curty and R. Buser

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 1, pages 398-407
Published in print March 2012 | ISSN: 0035-8711
Published online March 2012 | e-ISSN: 1365-2966 | DOI:
Gas and stellar metallicities in H ii galaxies

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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.

Keywords: ISM: abundances; galaxies: abundances; galaxies: evolution; galaxies: starburst

Journal Article.  7516 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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