Observational constraints on the progenitor metallicities of core-collapse supernovae
Abstract
We present constraints on the progenitor metallicities of core-collapse supernovae. To date, nearly all metallicity constraints have been inferred from indirect methods such as metallicity gradients in host galaxies, luminosities of host galaxies or derived global galaxy metallicities. Here, progenitor metallicities are derived from optical spectra taken at the sites of nearby supernovae, from the ratio of strong emission lines found in their host HII regions. We present results from the spectra of 74 host HII regions and discuss the implications that these have on the nature of core-collapse supernova progenitors.
Overall, while we find that the mean metallicity of Type Ibc environments is higher than that of Type II events, this difference is smaller than observed in previous studies. There is only a 0.06 dex difference in the mean metallicity values, at a statistical significance of ~1.5σ, while using a Kolmogorov-Smirnov test we find that the two metallicity distributions are marginally consistent with being drawn from the same parent population (probability >10 per cent). This argues that progenitor metallicity is not a dominant parameter in deciding supernovae type, with progenitor mass and/or binarity playing a much more significant role. The mean derived oxygen metallicities [12+log(O/H)] for the different supernova types, on the Pettini & Pagel scale, are 8.580 (standard error on the mean of 0.027) for the 46 Type II supernovae (dominated by Type II plateau), 8.616 (0.040) for 10 Type Ib and 8.626 (0.039) for 14 Type Ic. Overall, the Type Ibc supernovae have a mean metallicity of 8.635 (0.026, 27 supernovae). Hence, we find a slight suggestion of a metallicity sequence, in terms of increasing progenitor metallicity going from Type II through Ib and finally Ic supernovae arising from the highest metallicity progenitors. Finally we discuss these results in the context of all current literature progenitor metallicity measurements, and discuss biases and selection effects that may affect the current sample compared to overall supernova and galaxy samples. Based on observations made with the William Herschel Telescope (WHT) operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Institute de Astrofísica de Canarias; observations obtained with the Apache Point Observatory (APO) 3.5-m telescope, which is owned and operated by the Astrophysical Research Consortium; observations obtained with the Magellan Consortium's Clay Telescope; and observations obtained with the European Southern Observatory (ESO) New Technology Telescope (NTT), proposal ID: 077.C-0414. E-mail: anderson@das.uchile.cl- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2010
- DOI:
- 10.1111/j.1365-2966.2010.17118.x
- arXiv:
- arXiv:1006.0968
- Bibcode:
- 2010MNRAS.407.2660A
- Keywords:
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- supernovae: general;
- galaxies: abundances;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- ACCEPTED for publication in MNRAS