Gamma-ray bursts in normal and extreme star-forming galaxies

We discuss how gamma-ray burst (GRB) optical afterglows and multiwavelength observations of their host galaxies can be used to obtain information about the relative amounts of star formation happening in optical and submillimetre galaxies. That such an analysis will be possible follows from the currently favoured idea that GRBs are closely linked with high-mass star formation. Studying GRB host galaxies offers a method of finding low-luminosity submillimetre galaxies, which cannot be identified either in optical Lyman break surveys, because so much of their star formation is hidden by dust, or in submillimetre surveys, because their submillimetre fluxes are close to or below the confusion limit. Much of the star formation in the Universe could have occurred in such objects, so searching for them is an important exercise. From current observations, GRB host galaxies appear to be neither optically luminous Class-2 SCUBA galaxies like SMM J02399 - 0136 or SMM J14011 + 0252, nor galaxies containing dense molecular cores like local ultraluminous infrared galaxies (ULIGs), but rather some intermediate kind of galaxy. The host galaxy of GRB 980703 is a prototype of this kind of galaxy.