A VLT study of metal-rich extragalactic H II regions

Free access article

Issue		A&A Volume 441, Number 3, October III 2005


Page(s)		981 - 997
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20053369

A&A 441, 981-997 (2005)
DOI: 10.1051/0004-6361:20053369

I. Observations and empirical abundances

F. Bresolin¹, D. Schaerer^{2, 3}, R. M. González Delgado⁴ and G. Stasinska⁵

¹ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu 96822, USA
    e-mail: bresolin@ifa.hawaii.edu
² Observatoire de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
    e-mail: daniel.schaerer@obs.unige.ch
³ Laboratoire Astrophysique de Toulouse-Tarbes (UMR 5572), Observatoire Midi-Pyrénées, 14 avenue E. Belin, 31400 Toulouse, France
⁴ Instituto de Astrofísica de Andalucía (CSIC), Apdo. 3004, 18080 Granada, Spain
    e-mail: rosa@iaa.es
⁵ LUTH, Observatoire de Paris-Meudon, 5 place Jules Jansen, 92195 Meudon, France
    e-mail: grazyna.stasinska@obspm.fr

(Received 5 May 2005 / Accepted 3 June 2005)

Abstract
We have obtained spectroscopic observations from 3600 Åto 9200 Åwith FORS at the Very Large Telescope for approximately 70 H IIregions located in the spiral galaxies NGC 1232, NGC 1365, NGC 2903, NGC 2997 and NGC 5236. These data are part of a project to measure the chemical abundances and characterize the massive stellar content of metal-rich extragalactic H IIregions. In this paper we describe our dataset, and present emission line fluxes for the whole sample. In 32 H IIregions we measure at least one of the following auroral lines: [S II] $\,\lambda$ 4072, [N II] $\,\lambda$ 5755, [S III] $\,\lambda$ 6312 and [O II] $\,\lambda$ 7325. From these we derive electron temperatures, as well as oxygen, nitrogen and sulphur abundances, using classical empirical methods (both so-called " $T_{\rm e}$ -based methods" and "strong line methods"). Under the assumption that the temperature does not introduce severe biases, we find that the most metal-rich nebulae with detected auroral lines are found at 12 + log(O/H) $\simeq$ 8.9, i.e. about 60% larger than the adopted solar value. However, classical abundance determinations in metal-rich H IIregions may be severely biased and must be tested with realistic photoionization models. The spectroscopic observations presented in this paper will serve as a homogeneous and high-quality database for such purposes.

Key words: galaxies: abundances -- galaxies: ISM -- galaxies: stellar content

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