2007ApJ...656..186B -
Astrophys. J., 656, 186-197 (2007/February-2)
The oxygen abundance in the inner H II regions of M 101: implications for the calibration of strong-line metallicity indicators.
BRESOLIN F.
Abstract (from CDS):
I present deep spectroscopy of four H II regions in the inner, metal-rich zone of the spiral galaxy M101 obtained with the LRIS spectrograph at the Keck telescope. From the analysis of the collisionally excited lines in two of the target H II regions, H1013 and H493, I have obtained oxygen abundances 12+log(O/H)=8.52 and 12+log(O/H)=8.74, respectively. These measurements extend the determination of the oxygen abundance gradient of M101 via the direct method to only 3 kpc from the center. The intensity of the C II λ4267 line in H1013 leads to a carbon abundance 12+log(C/H)=8.66, corresponding to nearly twice the solar value. From a comparison of the continuum temperature derived from the Balmer discontinuity, T(Bac)=5000 K, and the line temperature derived from [O III] λ4363/λ5007, T[O III]=7700 K, an average temperature T0=5500 K and a mean square temperature fluctuation t2=0.06 have been derived. Accounting for the spatial inhomogeneity in temperature raises the oxygen abundance obtained from the oxygen auroral lines to 12+log(O/H)=8.93. These findings are discussed in the context of the calibration of strong-line metallicity indicators, in particular of the upper branch of R23. There is no evidence for the strong abundance biases arising from temperature gradients predicted theoretically for metal-rich H II regions.
Abstract Copyright:
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Journal keyword(s):
Galaxies: Abundances - Galaxies: Individual: Messier Number: M101 - Galaxies: ISM - ISM: Abundances
Simbad objects:
18
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