paper

Balmer jump temperature determination in a large sample of low-metallicity H II regions

arXiv:astro-ph/0701032 · doi:10.1051/0004-6361:20066067

Abstract

Aims. Continuing the systematic determination of the electron temperature of H II regions using the Balmer and/or Paschen discontinuities by Guseva et al. (2006) we focus here on 3.6m ESO telescope observations of a large new sample of 69 H II regions in 45 blue compact dwarf (BCD) galaxies. This data set spans a wide range in metallicity (Zsun/60<Z<Zsun/3) and, combined with the sample of 47 H II regions from Guseva et al. (2006), yields the largest spectroscopic data set ever used to derive the electron temperature in the H+ zone. Methods. In the same way as in Guseva et al. (2006) we have used a Monte Carlo technique to vary free parameters and to calculate a series of model spectral energy distributions (SEDs) for each H II region. The electron temperature in the H+ zones was derived from the best fitting synthetic and observed SEDs in the wavelength range ~3200-5100A, which includes the Balmer jump. Results. On the base of the present large spectroscopic sample we find that in hot (Te(H+)>11000 K) H II regions the temperature of the O2+ zone, determined from doubly ionised oxygen forbidden lines, does not differ statistically from the temperature of the H+ zone. Thus, we confirm and strengthen the finding by Guseva et al. (2006). We emphasize that due to a number of modelling assumptions and the observational uncertainties for individual objects, only a large, homogeneous sample, as the one used here, can enable a conclusive study of the relation between Te(H+) and Te(O III).

arXiv comment39 pages, 4 figures, accepted for publication in Astronomy and Astrophysics

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