GRB Host Studies (GHostS)

Gamma-ray bursts (GRBs) are the most energetic events in the universe, second only to the Big Bang. Discovered in the 1970s, their cosmological origin was revealed only in 1997, when the first distance (redshift) of a GRB was determined. This was GRB 970508 at redshift z = 0.835, exploded when the universe was about half of its present age.

Since then, the redshift was measured for 73 GRBs only (April 2006), though on average there is one event a day in the whole universe. The difficulty of determining the distance is connected to the fast fading of the blast, which generally disappears in a few days.

The goal of the GRB Host Studies (GHostS) is to investigate the properties of the galaxies hosting GRBs. Primarily, the project will focus on estimating the total mass, the rate of star formation and the chemical enrichment of the hosts, as well as the evolution of these parameters over cosmic time, and their differences with normal galaxies.

In previous studies, it has been found that GRB hosts are typically low massive galaxies forming stars at a high rate. Their relatively low chemical enrichment reveals their young ages. Samples under analysis are generally very small, due to the difficulty in acquiring data for faint objects. Whether metal rich, high mass and more quiescent GRB hosts are rare or just hard to find is not clear yet.

The GHostS is an archive collecting data on GRB host. At the moment this contains information for about half of all GRBs for which the distance was measured. More data will be included in the archive as they become public.