Abundance determinations in H II regions

Abstract

Abstract. The discrepancy between the oxygen abundances in high-metallicity H  regions determined through the T e -method (and/or through the corresponding "strong lines -oxygen abundance" calibration) and that determined through the model fitting (and/or through the corresponding "strong lines -oxygen abundance" calibration) is discussed. It is suggested to use the interstellar oxygen abundance in the solar vicinity, derived with very high precision from the high-resolution observations of the weak interstellar OIλ1356 absorption lines towards the stars, as a "Rosetta stone" to verify the validity of the oxygen abundances derived in H  regions with the T e -method at high abundances. The agreement between the value of the oxygen abundance at the solar galactocentric distance traced by the abundances derived in H  regions through the T e -method and that derived from the interstellar absorption lines towards the stars is strong evidence in favor of that i) the two-zone model for T e seems to be a realistic interpretation of the temperature structure within H  regions, and ii) the classic T e -method provides accurate oxygen abundances in H  regions. It has been concluded that the "strong lines -oxygen abundance" calibrations must be based on the H  regions with the oxygen abundances derived with the T e -method but not on the existing grids of the models for H  regions.

Abundance gradients in a sample of barred spiral galaxies

“…In particular, Liu et al (2000) derived abundances for the planetary nebula NGC 6153 from infrared emission lines (weakly sensitive to T e ), which are consistent with the ones from optical and ultraviolet emission lines, and this does the temperature fluctuation hypothesis increasingly doubtful. Moreover, at least for solar metallicities, the reliability of direct temperature determinations in H  regions seems to be confirmed, since a good agreement has been found between oxygen abundance determinations for nebulae in the solar neighborhood and ones derived from observations of the weak interstellar O λ1356 line towards the stars (Pilyugin 2003a;Moss et al 2002;Deharveng et al 2000;Rolleston et al 2000;Meyer et al 1998 Edmunds & Pagel (1984), what is expected since these authors also use photoionization models in their calibrations. However, the flatter O/H gradient obtained from our models for M 101 and NGC 1365 has important implications for empirical calibration of high abundances.…”

[Ar III]/[O III] and [S III]/[O III]: well-behaved oxygen abundance indicators for HII regions and star forming galaxies

“…This method is based on a thorough consideration of many factors, it has been widely discussed (Pilyugin 2001b(Pilyugin , 2003Cedrés et al 2004) and it is largely used. It is not clear at present whether more recent calibrations of the method (Pilyugin & Thuan 2005;Pilyugin et al 2006) are more accurate, because of the problem of abundance bias at high metallicity discussed in Stasińska (2005).…”

Influence of physical galaxy properties on Lyαescape in star-forming galaxies

“…For most of our galaxies, we measure the widely used abundance indicator, the R 23 index, which is based on the ratio ([Oii] λ3727 + [Oiii] λλ 4959, 5007)/Hβ (Pagel et al 1979;McGaugh 1991;Kobulnicky et al 1999;Pilyugin 2003). The main problem with the relationship (O/H)-R 23 is that there is a turnover around 12 + log(O/H) ∼ 8.4 that makes this index double-valued.…”