On the Distribution of Stellar Masses in Gamma-ray Burst Host Galaxies

Creators: Cerón, J. M. Castro; Michałowski, M. J.; Hjorth, J.; Malesani, D.; Gorosabel, J.; Watson, D.; Fynbo, J. P. U.; Calderón, M. Morales

Abstract

We analyze Spitzer images of 30 long-duration gamma-ray burst (GRB) host galaxies. We estimate their total stellar masses (M_*) based on the rest-frame K-band luminosities (L_K_(rest)) and constrain their star formation rates (SFRs; not corrected for dust extinction) based on the rest-frame UV continua. Further, we compute a mean M_*/ L_K_(rest) = 0.45 M_☉/L_☉. We find that the hosts are low M_*, star-forming systems. The median M_* in our sample ( = 10^(9.7) M_☉) is lower than that of "field" galaxies (e.g., Gemini Deep Deep Survey). The range spanned by M_* is 10^7 M_☉ < M_* < 10^(11) M_☉, while the range spanned by the dust-uncorrected UV SFR is 10^(–2) M_☉ yr^(–1) < SFR < 10 M_☉ yr^(–1). There is no evidence for intrinsic evolution in the distribution of M_* with redshift. We show that extinction by dust must be present in at least 25% of the GRB hosts in our sample and suggest that this is a way to reconcile our finding of a relatively lower UV-based, specific SFR (φ ≡ SFR/M_*) with previous claims that GRBs have some of the highest φ values. We also examine the effect that the inability to resolve the star-forming regions in the hosts has on φ.

Additional Information

© 2010 American Astronomical Society. Received 2008 March 12; accepted 2010 May 24; published 2010 September 14. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. We thank Ranga-Ram Chary, Árdís Elíasdóttir, Peter Laursen, Bo Milvang-Jensen, and Paul M. Vreeswijk for insightful comments. The Dark Cosmology Centre is funded by the Danish National Research Foundation. J.M.C.C. gratefully acknowledges support from the Instrumentcenter for Dansk Astrofysik and the Niels Bohr Instituttet's International PhD School of Excellence as well as from the ESA Research Fellowship in Space Science Programme. J.G. was funded in part by Spain's AyA 2.004-01.515 and ESP 2.005-07.714-C03-03 grants. The authors acknowledge the data analysis facilities provided by the Starlink Project which is run by CCLRC on behalf of PPARC. This research has made use of: the NASA's Astrophysics Data System; the GHostS database (http://www.grbhosts.org/), which is partly funded by Spitzer/NASA grant RSA Agreement No. 1287913; the Gamma-Ray Burst Afterglows site (http://www.mpe.mpg.de/∼jcg/grb.html), which is maintained by Jochen Greiner; IRAF, distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation; the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration; and SAOImage DS9, developed by the Smithsonian Astrophysical Observatory. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d'Etudes Spatiales of France and the Korean Ministry of Science and Technology. Facilities: Spitzer (IRAC), GALEX (NUV).

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