Journal Article

Revisiting the metallicity of long-duration gamma-ray burst host galaxies: the role of chemical inhomogeneity within galaxies

Y. Niino

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 417, issue 1, pages 567-572
Published in print October 2011 | ISSN: 0035-8711
Published online October 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19299.x
Revisiting the metallicity of long-duration gamma-ray burst host galaxies: the role of chemical inhomogeneity within galaxies

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We predict the metallicity probability distribution function (PDF) of long gamma-ray burst (GRB) host galaxies at low redshifts (z≲ 0.3) when GRBs occur only in low-metallicity environments, assuming empirical formulations of galaxy properties. We discuss the contribution of high-metallicity galaxies to the cosmic rate of low-metallicity GRBs, taking the internal dispersion of metallicity within each galaxy into account. Assuming that GRBs trace low-metallicity star formation <Zcrit: 12+log10(O/H) = 8.2, we find that GRB host galaxies may have systematically higher metallicity than GRB progenitors. Furthermore, we expect >rsim10 per cent of the host galaxies to have 12+log10(O/H) > 8.8, if galaxies have an internal dispersion of metallicity comparable to that observed in the Milky Way. Our results show that the low-metallicity scenario of GRB progenitors can be reconciled with recent discoveries of the high-metallicity host galaxies of GRBs. We also show a possible bimodality in the host metallicity PDF that results from the single-progenitor model of GRBs. If found in future observations, the bimodality might be a clue to constrain the nature of GRB progenitors.

Keywords: galaxies: abundances; gamma-ray burst: general

Journal Article.  3552 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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