Chary, R. and Berger, E. and Cowie, L. (2007) Spitzer Observations of Gamma-Ray Burst Host Galaxies: A Unique Window into High-Redshift Chemical Evolution and Star Formation. Astrophysical Journal, 671 (1). pp. 272-277. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20100430-103449713
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We present deep 3.6 μm observations of three z ~ 5 GRB host galaxies with the Spitzer Space Telescope. The host of GRB 060510B, at z = 4.942, is detected with a flux density of 0.23 ± 0.04 μJy, corresponding to a rest-frame V-band luminosity of 1.3 × 10^(10) L_☉, or ≈0.15 L_(*,V,z=3). We do not detect the hosts of GRBs 060223A and 060522 and constrain their rest-frame V-band luminosity to <0.1 L_(*,V,z=3). Our observations reveal that z ~ 5 GRB host galaxies are a factor of ~3 less luminous than the median luminosity of spectroscopically confirmed z ~ 5 galaxies in the Great Observatories Origins Deep Survey and the Hubble Ultra Deep Field. The strong connection between GRBs and massive star formation implies that not all star-forming galaxies at these redshifts are currently being accounted for in deep surveys and GRBs provide a unique way to measure the contribution to the star formation rate density from galaxies at the faint end of the galaxy luminosity function. By correlating the comoving star formation rate density with comoving GRB rates at lower redshifts, we estimate a lower limit to the star formation rate density of 0.12 ± 0.09 and 0.09 ± 0.05 M_☉ yr(-1) Mpc^(-3) at z ~ 4.5 and z ~ 6, respectively. This is in excellent agreement with extinction-corrected estimates from Lyman break galaxy samples. Finally, our observations provide initial evidence that the metallicity of star-forming galaxies evolves more slowly than the stellar mass density between z ~ 5 and z ~ 0, probably indicative of the loss of a significant fraction of metals to the intergalactic medium, especially in low-mass galaxies.
|Additional Information:||© 2007 American Astronomical Society. Received 2007 May 24; accepted 2007 August 17. We wish to thank Mark Dickinson for his comments, which strengthened the arguments in this paper. We also acknowledge the extensive resources that are invested by the entire GRB community, not all of whom can be cited here, which enables prompt imaging and spectroscopic follow-up of the bursts. This work is based 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. Support for this work was provided by NASA through an award issued by JPL/Caltech. E. B. acknowledges support by NASA through Hubble Fellowship grantHST-01171.01 awarded by STSCI, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS5-26555.|
|Subject Keywords:||cosmology: observations; galaxies: abundances; galaxies: high-redshift; galaxies: starburst; gamma-rays: bursts|
|Official Citation:||R. Chary et al 2007 ApJ 671 272 doi: 10.1086/522692|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||30 Apr 2010 20:12|
|Last Modified:||26 Dec 2012 11:59|
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