A Submillimeter and Radio Survey of Gamma-Ray Burst Host Galaxies A Glimpse into the Future

We present the first comprehensive search for submillimeter and radio emission from the host galaxies of twenty well-localized gamma-ray bursts (GRBs). With the exception of a single source, all observations were undertaken months to years after the GRB ex

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aASubmillimeterandRadioSurveyofGamma-RayBurstHostGalaxies:AGlimpseintotheFutureofStarFormationStudiesE.Berger1,L.L.Cowie2,S.R.Kulkarni1,D.A.Frail3,H.Aussel2,&A.J.Barger2,4,5ABSTRACTWepresentthe rstcomprehensivesearchforsubmillimeterandradioemis-sionfromthehostgalaxiesoftwentywell-localizedγ-raybursts(GRBs).Withtheexceptionofasinglesource,allobservationswereundertakenmonthstoyearsaftertheGRBexplosionstoensurenegligiblecontaminationfromtheafterglows.WedetectthehostgalaxyofGRB000418inboththesub-mmandradio,andthehostgalaxyofGRB000210onlyinthesub-mm.Theseobservations,incon-junctionwiththepreviousdetectionsofthehostgalaxiesofGRB980703andGRB010222,indicatethatabout20%ofGRBhostgalaxiesareultra-luminous(L>1012L⊙)andhavestarformationratesofabout500M⊙yr 1.Asanen-semble,thenon-detectedhostshaveastarformationrateofabout100M⊙yr 1(5σ)basedontheirradioemission.Thedetectedandensemblestarformationratesexceedtheoptically-determinedvaluesbyanorderofmagnitude,indicat-ingsigni cantdustobscuration.Inthesamevein,theratioofbolometricdustluminositytoUVluminosityforthehostsdetectedinthesub-mmandradiorangesfrom~20 800,andfollowstheknowntrendofincreasingobscurationwithincreasingbolometricluminosity.Wealsoshowthat,bothasasampleandindividually,theGRBhostgalaxieshavebluerR Kcolorsascomparedwithgalaxiesselectedinthesub-mminthesameredshiftrange.Thispossiblyin-dicatesthatthestellarpopulationsintheGRBhostsareonaverageyounger,

supportingthemassivestellarprogenitorscenarioforGRBs,butitisalsopossiblethatGRBhostsareonaveragelessdusty.Beyondthespeci cresultspresented

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