Journal Article

Predictions of the extent of self-enrichment in oxygen of giant metal-poor H <span class="smallCaps">ii</span> regions

Aida Wofford

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 395, issue 2, pages 1043-1054
Published in print May 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI:
Predictions of the extent of self-enrichment in oxygen of giant metal-poor H ii regions

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In general, H ii regions do not show clear signs of self-enrichment in products from massive stars (M≥ 8 M). In order to explore why I modelled the contamination with Wolf–Rayet star ejecta of metal-poor (Z= 0.001) H ii regions, ionized either by a 106 M cluster of coeval stars (cluster 1) or by a cluster resulting from continuous star formation at a rate of 1 M yr−1 (cluster 2). The clusters have Z= 0.001 and a Salpeter initial mass function from 0.1 to 120 M. Independent one-dimensional constant density simulations of the emission-line spectra of unenriched H ii regions were computed at the discrete ages 1, 2, 3, 4 and 5 Myr, with the photoionization code cloudy, using as input, radiative and mechanical stellar feedbacks predicted by the evolutionary synthesis code starburst99. Each H ii region was placed at the outer radius of the adiabatically expanding superbubble of Mac Low & McCray. For models with thermal and ionization balance time-scales of less than 1 Myr, and with oxygen emission-line ratios in agreement with observations, the volume of the superbubble and the H ii region was uniformly and instantaneously polluted with stellar ejecta predicted by starburst99. I obtained a maximum oxygen abundance enhancement of 0.025 dex, with cluster 1, at 4 Myr. It would be unobservable.

Keywords: stars: early-type; ISM: abundances; ISM: bubbles; ISM: evolution; H ii regions

Journal Article.  10175 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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