Gamma-ray burst host galaxies at low and high redshift
  The galaxies hosting the most energetic explosions in the universe, the
gamma-ray bursts (GRBs), are generally found to be low-mass, metal poor, blue
and star forming galaxies. However, the majority of the targets investigated so
far (less than 100) are at relatively low redshift, z < 2. We know that at low
redshift, the cosmic star formation is predominantly in small galaxies.
Therefore, at low redshift, long-duration GRBs, which are associated with
massive stars, are expected to be in small galaxies. Preliminary investigations
of the stellar mass function of z < 1.5 GRB hosts does not indicate that these
galaxies are different from the general population of nearby star-forming
galaxies. At high-z, it is still unclear whether GRB hosts are different.
Recent results indicate that a fraction of them might be associated with dusty
regions in massive galaxies. Remarkable is the a super-solar metallicity
measured in the interstellar medium of a z = 3.57 GRB host.
