Precision abundance analysis of bright H ii galaxies |
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| Authors: | Guillermo F Hägele † Ángeles I Díaz ‡ Elena Terlevich § Roberto Terlevich ‡ Enrique Pérez-Montero ¶ Mónica V Cardaci |
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| Institution: | Departamento de Física Teórica, C-XI, Universidad Autónoma de Madrid, 28049 Madrid, Spain;INAOE, Tonantzintla, Apdo. Postal 51, 72000 Puebla, México;Laboratoire d'Astrophysique de Toulouse-Tarbes, Observatoire Midi-Pyrénées 14, avenue Edouard Belin, 31400 Toulouse, France;XMM Science Operations Centre, European Space Astronomy Centre of ESA, PO Box 50727, 28080 Madrid, Spain |
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| Abstract: | We present high signal-to-noise ratio spectrophotometric observations of seven luminous H ii galaxies. The observations have been made with the use of a double-arm spectrograph which provides spectra with a wide wavelength coverage, from 3400 to 10 400 Å free of second-order effects, of exactly the same region as that of a given galaxy. These observations are analysed applying a methodology designed to obtain accurate elemental abundances of oxygen, sulphur, nitrogen, neon, argon and iron in the ionized gas. Four electron temperatures and one electron density are derived from the observed forbidden line ratios using the five-level atom approximation. For our best objects, errors of 1 per cent in t e(O iii ]), 3 per cent in t e(O ii ]) and 5 per cent in t e(S iii ]) are achieved with a resulting accuracy of 7 per cent in total oxygen abundances, O/H.
The ionization structure of the nebulae can be mapped by the theoretical oxygen and sulphur ionic ratios, on the one side, and the corresponding observed emission line ratios, on the other – the η and η' plots. The combination of both is shown to provide a means to test photoionization model sequences presently applied to derive elemental abundances in H ii galaxies. |
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| Keywords: | ISM: abundances H ii regions galaxies: abundances galaxies: fundamental parameters galaxies: starburst |
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