Main Astronomical Observatory, Ukrainian National Academy of Sciences, Zabolotnoho 27, Kyiv 03680, Ukraine e-mail: email@example.com
2 Instituto de Astrofísica de Andalucía, Apdo. 3004, 18080 Granada, Spain
3 Institute for Astrophysics, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
Accepted: 21 December 2006
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, ApJ, 644, 890) we focus here on 3.6 m 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 () 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 ~3200–5100 Å, which includes the Balmer jump.
Results.On the base of the present large spectroscopic sample we find that in hot (Te(H+) 11 000 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).
Key words: galaxies: irregular / galaxies: starburst / galaxies: ISM / galaxies: abundances
Based on observations collected at the European Southern Observatory, Chile, ESO program 76.B-0739.
© ESO, 2007