R. Stoll, J. L. Prieto, K. Z. Stanek, R. W. Pogge
Type II SNe can be used as a star formation tracer to probe the metallicity distribution of global low-redshift star formation. We present oxygen and iron abundance distributions of type II supernova progenitor regions that avoid many previous sources of bias, and can serve as a standard of comparison for properly observationally evaluating how different classes of supernovae depend on progenitor metallicity. In contrast to previous supernova host metallicity studies, this sample is homogeneous and is drawn from an areal rather than a targeted survey, so supernovae in the lowest-mass galaxies are not excluded. We spectroscopically measure the gas-phase oxygen abundance near a representative subsample of the hosts of type II supernovae from the first-year Palomar Transient Factory (PTF) supernova search. The median metallicity is 12+log(O/H) = 8.65 and the median host galaxy stellar mass from fits to SDSS photometry is 10^9.9 solar masses. Though iron abundance is more central to the evolution of massive stars than oxygen abundance, it cannot be measured directly in extragalactic HII regions. Using the relationship between iron and oxygen abundances found for Milky Way disk, bulge, and halo stars, we can translate our distribution of type II SN environments as a function of oxygen abundance into an estimate of the iron abundance, and find the median [Fe/H] = -0.60.
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http://arxiv.org/abs/1205.2338
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