Journal Article

Multiple ionization sources in H <span class="smallCaps">ii</span> regions and their effect on derived nebular abundances

B. Ercolano, R. Wesson and N. Bastian

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 401, issue 2, pages 1375-1380
Published in print January 2010 | ISSN: 0035-8711
Published online January 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15743.x
Multiple ionization sources in H ii regions and their effect on derived nebular abundances

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We present a theoretical investigation of the effect of multiple ionization sources in H ii regions on the total elemental abundances derived from the analysis of collisionally excited emission lines. We focus on empirical methods based on direct temperature measurements that are commonly employed in cases when the temperature of the nebular gas can be determined from the ratio of nebular to auroral lines of (e.g.) doubly ionized oxygen. We find that direct temperature methods that employ a two-temperature zone approach (DT2T methods) are very robust against the spatial distribution of sources. Errors smaller than 0.15 dex are estimated for regions where the metallicity is twice solar and errors below 0.05 dex for solar metallicities and below. The biases introduced by the spatial distribution of the ionization sources are thus much smaller for DT2T methods than for strong line methods, previously investigated by Ercolano, Bastian & Stasińska. Our findings are in agreement with the recent study of H ii regions in NGC 300 by Bresolin et al.

Keywords: ISM: abundances; H ii regions; galaxies: abundances; galaxies: ISM

Journal Article.  3875 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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