Chemical abundances and spatial distribution of Long Gamma-Ray Bursts
  We analyse the spatial distribution within host galaxies and chemical
properties of the progenitors of Long Gamma Ray Bursts as a function of
redshift. By using hydrodynamical cosmological simulations which include star
formation, Supernova feedback and chemical enrichment and based on the
hypothesis of the collapsar model with low metallicity, we investigate the
progenitors in the range 0 < z < 3. Our results suggest that the sites of these
phenomena tend to be located in the central regions of the hosts at high
redshifts but move outwards for lower ones. We find that scenarios with low
metallicity cut-offs best fit current observations. For these scenarios Long
Gamma Ray Bursts tend to be [Fe/H] poor and show a strong alpha-enhancement
evolution towards lower values as redshift decreases. The variation of typical
burst sites with redshift would imply that they might be tracing different part
of galaxies at different redshifts.
