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The Star Formation Rate and Metallicity of the Host Galaxy of the Dark GRB 080325 at z=1.78

Hashimoto, Tetsuya and Perley, Daniel A. and Ohta, Kouji and Aoki, Kentaro and Tanaka, Ichi and Niino, Yuu and Yabe, Kiyoto and Kawai, Nobuyuki (2015) The Star Formation Rate and Metallicity of the Host Galaxy of the Dark GRB 080325 at z=1.78. Astrophysical Journal, 806 (2). Art. No. 250. ISSN 0004-637X.

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We present near-infrared spectroscopy of the host galaxy of the dark gamma-ray burst (GRB) 080325 using Subaru/Multi-Object Infrared Camera and Spectrograph. The obtained spectrum provides a clear detection of Hα emission and marginal [Nii]λ6584. The host is a massive (M_* ~ 10^(11) M_⊙), dusty (A_V ~ 1.2) star-forming galaxy at z = 1.78. The extinction-corrected star formation rate (SFR) calculated from the Hα luminosity (35.6–47.0 M_⊙ yr^(−1)) is typical among GRB host galaxies (and star-forming galaxies generally) at z>1; however, the specific SFR is lower than for normal star-forming galaxies at redshift ~1.6, in contrast to the high specific SFR measured for many of other GRB hosts. The metallicity of the host is estimated to be 12 + log(O/H)_(KK04) = 8.88. We emphasize that this is one of the most massive host galaxies at z>1 for which metallicity is measured with emission-line diagnostics. The metallicity is fairly high among GRB hosts, however, this is still lower than the metallicity of normal star-forming galaxies of the same mass at z ~ 1.6. The metallicity offset from normal star-forming galaxies is close to a typical value of other GRB hosts and indicates that GRB host galaxies are uniformly biased toward low metallicity over a wide range of redshifts and stellar masses. The low-metallicity nature of the GRB 080325 host likely cannot be attributed to the fundamental metallicity relation of star-forming galaxies because it is a metal-poor outlier from the relation and has a low specific star formation rate. Thus, we conclude that metallicity is important to the mechanism that produced this GRB.

Item Type:Article
Related URLs:
URLURL TypeDescription
Perley, Daniel A.0000-0001-8472-1996
Kawai, Nobuyuki0000-0001-9656-0261
Additional Information:© 2015 American Astronomical Society. Received 2014 November 11; accepted 2015 March 23; published 2015 June 22. We thank the Subaru Telescope staff for their invaluable help for our observation with Subaru/MOIRCS. Work by T.H. was supported by funding from the National Astronomical Observatory of Japan and the TMT project office in Japan. T.H. acknowledges the Department of Astronomy, California Institute of Technology for providing an excellent academic research environment for writing the paper and also thanks S. R. Kulkarni and T. Usuda for creating the opportunity for this collaborative study.
Group:Thirty Meter Telescope
Funding AgencyGrant Number
National Astronomical Observatory of JapanUNSPECIFIED
TMT project office in JapanUNSPECIFIED
Subject Keywords:galaxies: abundances; gamma-ray burst: individual (GRB 080325)
Issue or Number:2
Record Number:CaltechAUTHORS:20150805-090759718
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Official Citation:The Star Formation Rate and Metallicity of the Host Galaxy of the Dark GRB 080325 at z=1.78 Tetsuya Hashimoto et al. 2015 ApJ 806 250
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59199
Deposited By: Ruth Sustaita
Deposited On:05 Aug 2015 22:18
Last Modified:09 Mar 2020 13:18

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