干旱区生态环境知识资源中心

Long-duration gamma-ray burs are produced in the death of young, massive stars. GRBs thus provide a precious cosmological tool, since they pinpoint locations in the Universe where active star formation is ongoing. We describe here the preparation and collection of a large, unbiased sample of GRB host galaxies. The goals of our program are the very discovery of the hosts, the search for reddened systems, the determination of redshifts, and the study of the Ly alpha emission. Preliminary results include a large detection rate in the optical, a low fraction of red systems, an increase of the redshift completeness (including several systems in the "redshift desert"), and a lower-then-expected recovery of Ly alpha emission.