Probing Cosmic Star Formation Using Long Gamma-Ray Bursts: New Constraints from the Spitzer Space Telescope

• Published in: The Astrophysical journal Vol. 642; no. 2; pp. 636 - 652
• Main Authors: Le Floc’h, Emeric, Charmandaris, Vassilis, Forrest, William J, Mirabel, I. Félix, Armus, Lee, Devost, Daniel
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 10.05.2006; University of Chicago Press; American Astronomical Society
• Subjects: Astronomy; Astrophysics; Earth, ocean, space; Exact sciences and technology; Physics; galaxies: individual (GRB 970828, GRB 980425, GRB 980613, GRB 980703, GRB 981226, GRB 990705); Red shift; infrared: galaxies; Star formation; Cosmic gamma sources; Cosmology; Infrared galaxies; Gamma ray burst; cosmology: observations; galaxies: high-redshift
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/501118

We report on IRAC 4.5 m, IRAC 8.0 m, and MIPS 24 m deep observations of 16 gamma-ray burst (GRB) host galaxies performed with the Spitzer Space Telescope, and we investigate in the thermal infrared the presence of evolved stellar populations and dust-enshrouded star-forming activity associated with these objects. Our sample is derived from GRBs that were identified with subarcsecond localization between 1997 and 2001, and only a very small fraction (20%) of the targeted sources are detected down to f sub(4.5 m) 3.5 Jy and f sub(24 m) 85 Jy (3). This likely argues against a population dominated by massive and strongly starbursting (i.e., SFR 100 M yr super(-1)) galaxies as has been recently suggested from submillimeter/radio and optical studies of similarly selected GRB hosts. Furthermore, we find evidence that some GRBs do not occur in the most infrared luminous regions--hence the most actively star-forming environments--of their host galaxies. Should the GRB hosts be representative of all star-forming galaxies at high redshift, models of infrared galaxy evolution indicate that 50% of GRB hosts should have f sub(24 m) 100 Jy. Unless the identification of GRBs prior to 2001 was prone to strong selection effects biasing our sample against dusty galaxies, we infer in this context that the GRBs identified with the current techniques cannot be directly used as unbiased probes of the global and integrated star formation history of the universe.