TY - JOUR
T1 - The optically unbiased GRB host (TOUGH) survey. VI. Radio observations at z < 1 and consistency with typical star-forming galaxies
AU - Michalowski...[et al.], Michal
AU - Hjorth, Jens
AU - Malesani, Daniele
AU - Castro Cerón, José María
AU - Fynbo, Johan Peter Uldall
AU - Sollerman, Jesper Olof
AU - Watson, Darach Jafar
PY - 2012/8/20
Y1 - 2012/8/20
N2 - The objective of this paper is to determine the level of obscured star formation activity and dust attenuation in a sample of gamma-ray burst (GRB) hosts, and to test the hypothesis that GRB hosts have properties consistent with those of the general star-forming galaxy populations. We present a radio continuum survey of all z < 1 GRB hosts in The Optically Unbiased GRB Host (TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN hosts discovered before 2006 October. We present new radio data for 22 objects and have obtained a detection for three of them (GRB 980425, 021211, 031203; none in the TOUGH sample), increasing the number of radio-detected GRB hosts from two to five. The star formation rate (SFR) for the GRB 021211 host of 825 M yr-1, the highest ever reported for a GRB host, places it in the category of ultraluminous infrared galaxies. We found that at least 63% of GRB hosts have SFR < 100 M yr-1 and at most 8% can have SFR > 500 M yr-1. For the undetected hosts the mean radio flux (<35 μJy 3σ) corresponds to an average SFR < 15 M yr-1. Moreover, ≳ 88% of the z ≲ 1 GRB hosts have ultraviolet dust attenuation A UV < 6.7 mag (visual attenuation AV < 3 mag). Hence, we did not find evidence for large dust obscuration in a majority of GRB hosts. Finally, we found that the distributions of SFRs and A UV of GRB hosts are consistent with those of Lyman break galaxies, Hα emitters at similar redshifts, and of galaxies from cosmological simulations. The similarity of the GRB population with other star-forming galaxies is consistent with the hypothesis that GRBs, a least at z ≲ 1, trace a large fraction of all star formation, and are therefore less biased indicators than once thought.
AB - The objective of this paper is to determine the level of obscured star formation activity and dust attenuation in a sample of gamma-ray burst (GRB) hosts, and to test the hypothesis that GRB hosts have properties consistent with those of the general star-forming galaxy populations. We present a radio continuum survey of all z < 1 GRB hosts in The Optically Unbiased GRB Host (TOUGH) sample supplemented with radio data for all (mostly pre-Swift) GRB-SN hosts discovered before 2006 October. We present new radio data for 22 objects and have obtained a detection for three of them (GRB 980425, 021211, 031203; none in the TOUGH sample), increasing the number of radio-detected GRB hosts from two to five. The star formation rate (SFR) for the GRB 021211 host of 825 M yr-1, the highest ever reported for a GRB host, places it in the category of ultraluminous infrared galaxies. We found that at least 63% of GRB hosts have SFR < 100 M yr-1 and at most 8% can have SFR > 500 M yr-1. For the undetected hosts the mean radio flux (<35 μJy 3σ) corresponds to an average SFR < 15 M yr-1. Moreover, ≳ 88% of the z ≲ 1 GRB hosts have ultraviolet dust attenuation A UV < 6.7 mag (visual attenuation AV < 3 mag). Hence, we did not find evidence for large dust obscuration in a majority of GRB hosts. Finally, we found that the distributions of SFRs and A UV of GRB hosts are consistent with those of Lyman break galaxies, Hα emitters at similar redshifts, and of galaxies from cosmological simulations. The similarity of the GRB population with other star-forming galaxies is consistent with the hypothesis that GRBs, a least at z ≲ 1, trace a large fraction of all star formation, and are therefore less biased indicators than once thought.
U2 - 10.1088/0004-637X/755/2/85
DO - 10.1088/0004-637X/755/2/85
M3 - Journal article
SN - 0004-637X
VL - 755
SP - 85
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
ER -