RECALIBRATION OF PAGEL’S METHOD FOR H II REGIONS CONSIDERING THE THERMAL STRUCTURE, THE IONIZATION STRUCTURE, AND THE DEPLETION OF O INTO DUST GRAINS

María A. Peña-Guerrero, Antonio Peimbert & Manuel Peimbert (Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, México 04510 D.F., Mexico)

Using a sample of 28 HII regions from the literature with measured temperature inhomogeneity parameter, t^2, we present a statistical correction to the chemical abundances determined with the direct method. We used the t^2 values to correct the oxygen gaseous abundances and consider the oxygen depletion into dust to calculate the total abundances for these objects. This correction is used to obtain a new calibration of Pagel’s strong-line method to determine oxygen abundances in HII regions. Our new calibration simultaneously considers the temperature structure, the ionization structure, and the fraction of oxygen depleted into dust grains. Previous calibrations in the literature have included one or two of these factors; this is the first time all three are taken into account. This recalibration conciliates the systematic differences among the temperatures found from different methods. We find that the total correction due to thermal inhomogeneities and dust depletion amounts to an increase in the O/H ratio of HII regions by factors of 1.7 to 2.2 (or 0.22 to 0.35 dex). This result has important implications in various areas of astrophysics such as the study of the higher end of the initial mass function, the star formation rate, and the mass-metallicity relation of galaxies, among others.

Complete preprint ==> http://arxiv.org/abs/1204.4446

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