Berger, E. and Fox, D. B. and Kulkarni, S. R. and Frail, D. A. and Djorgovski, S. G. (2007) The ERO Host Galaxy of GRB 020127: Implications for the Metallicity of GRB Progenitors. Astrophysical Journal, 660 (1). pp. 504-508. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20091019-104150426
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We present optical and near-IR observations of the host galaxy of GRB 020127, for which we measure R - K_s = 6.2 mag. This is only the second GRB host to date classified as an ERO. The spectral energy distribution (SED) is typical of a dusty starburst galaxy, with a redshift z ≈ 1.9, a luminosity L ≈ 5L^*, and an inferred stellar mass of M_* ~ 10^(11)-10^(12) M_⊙, two orders of magnitude more massive than typical GRB hosts. A comparison to the z ~ 2 mass-metallicity (M-Z) relation suggests that the host metallicity is about 0.5-1Z_⊙. This result shows that at least some GRBs occur in massive, metal-enriched galaxies, and that the proposed low-metallicity bias of GRB progenitors is not as severe as previously claimed. Instead, we propose that the blue colors and sub-L^* luminosities of most GRB hosts reflect their young starburst populations. This explanation also accounts for the prevalence of low-redshift GRBs in low-mass galaxies, since star formation activity shifts from high- to low-mass galaxies as a function of decreasing redshift ("downsizing"). Thus, the low-metallicity bias claimed for z ≾ 0.2 GRB hosts is likely a secondary effect, which reflects the M-Z relation, and consequently GRBs and their hosts may serve as a reliable tracer of cosmic star formation activity.
|Additional Information:||© 2007 The American Astronomical Society. Received 2006 September 5; accepted 2007 January 21. We thank J. Kollmeier, D. Erb, and the anonymous referee for helpful comments on the manuscript. E. B. is supported by NASA through Hubble Fellowship grant HST-01171.01 awarded by STScI, which is operated by AURA, Inc. for NASA under contract NAS5-26555. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.|
|Subject Keywords:||galaxies: starburst; gamma rays: bursts|
|Official Citation:||The ERO Host Galaxy of GRB 020127: Implications for the Metallicity of GRB Progenitors E. Berger, D. B. Fox, S. R. Kulkarni, D. A. Frail, and S. G. Djorgovski 2007 ApJ 660 504-508 doi: 10.1086/513007|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||26 Oct 2009 18:18|
|Last Modified:||26 Dec 2012 11:29|
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