The SKA contribution to GRB cosmology

Abstract

Although they are not standard candles, the use of Gamma–Ray Bursts (GRBs) as a tool formeasuring the geometry and expansion rate of the Universe is strongly motivated by their uniquecombination of huge luminosities, up to more than 1053erg/s, with a redshift distribution ex-tending up to more thanz= 9. Several attempts to exploit the correlation between the photonenergy at which the spectral energy distribution peaks (peak energy) and the radiated energy (orluminosity) for standardizing GRBs and to use them to estimate cosmological parameters havebeen made. These studies show that with the present data–set, GRBs can provide a significantand independent confirmation ofΩM∼0.3 for a flatΛCDM. The SKA, through its unprecedentedcapabilities of characterizing the radio afterglow light-curve from the peak emission up to thetransition to non–relativistic regime for a significant fraction of GRBs, and in combination withmeasurements from next generation GRB experimens, will provide unique clues on the collima-tion angles and energy budget of these events, thus reducing significantly the dispersion of thepeak energy–radiated energycorrelation and improving its reliability and accuracy in investigat-ing dark energy properties and evolution