SCUBA Observations of the Host Galaxies of Gamma-Ray Bursts

In recent years, a population of galaxies with huge infrared luminosities and dust masses has been discovered in the submillimetre. Observations suggest that the AGN contribution to the luminosities of these submillimetre-selected galaxies is low; instead their luminosities are thought to be mainly due to strong episodes of star formation following merger events. Our current understanding of GRBs as the endpoints in the life of massive stars suggest that they will be located in such galaxies. We have observed a sample of well-located GRB host galaxies in the submillimetre. Comparing the results with the general submillimetre-selected galaxy population, we find that at low fluxes (S850 4 mJy), the two agree well. However, there is a lack of bright GRB hosts in the submillimetre. This finding is reinforced when the results of other groups are included. Possible explanations are discussed. These results help us assess the roles of both GRB host galaxies and submillimetreselected galaxies in the evolution of the Universe. STAR FORMATION IN THE SUBMILLIMETRE Our understanding of galaxy evolution was revolutionised by the observations of the IRAS satellite [1], which revealed large populations of dust-enshrouded, actively starforming galaxies in the local Universe. This picture was extended to high redshifts by several instruments, predominantly the Submillimetre Common-User Bolometer Array (SCUBA, [2]) on the James Clerk Maxwell Telescope (JCMT). SCUBA observes simultaneously at 450 and 850 μm and hence is sensitive to emission from dust, heated to 40 K by optical and UV light form stars. SCUBA’s unique sensitivity to submillimetre (submm) radiation is enhanced by the negative k-correction suffered by the greybody radiation, which makes SCUBA almost equally able to see galaxies at z of 1 and 10. SCUBA has now discovered in excess of 200 galaxies; however progress in understanding these objects has been relatively slow. Identification of the SCUBA galaxies at optical wavelengths is hampered by two factors. Firstly, SCUBA galaxies are inherently CP727, Gamma-Ray Bursts: 30 Years of Discovery, edited by E. E. Fenimore and M. Galassi © 2004 American Institute of Physics 0-7354-0208-6/04/$22.00