Journal Article

‘Counterpart’ method for abundance determinations in H <span class="smallCaps">ii</span> regions

L. S. Pilyugin, E. K. Grebel and L. Mattsson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 424, issue 3, pages 2316-2329
Published in print August 2012 | ISSN: 0035-8711
Published online August 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21398.x
‘Counterpart’ method for abundance determinations in H ii regions

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Abstract

We suggest a new way of determining abundances and electron temperatures in H ii regions from strong emission lines. Our approach is based on the standard assumption that H ii regions with similar intensities of strong emission lines have similar physical properties and abundances. A ‘counterpart’ for a studied H ii region may be chosen among H ii regions with well-measured abundances (reference H ii regions) by comparison of carefully chosen combinations of strong-line intensities. Then the abundances in the investigated H ii region can be assumed to be the same as those in its counterpart. In other words, we suggest to determine the abundances in H ii regions ‘by precedent’. To get more reliable abundances for the considered H ii region, a number of reference H ii regions are selected and then the abundances in the target H ii region are estimated through extrapolation/interpolation. We will refer to this method of abundance determination as the counterpart method or, for brevity, the C method. We define a sample of reference H ii regions and verify the validity of the C method. We find that this method produces reliable abundances. Finally, the C method is used to obtain the radial abundance distributions in the extended discs of the spiral galaxies M83, NGC 4625 and NGC 628.

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

Journal Article.  10278 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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