Long Gamma Ray Bursts Trace The Star Formation History
  We show that if the broad-line supernova explosions of type Ic (SNeIc)
produce the bulk of the observed long duration gamma ray bursts (LGRBs), which
include the high luminosity GRBs, low luminosity GRBs and X-ray flashes (XRFs),
and if LGRBs have the geometry assumed in the cannonball (CB) model of LGRBs,
then their rate measured by Swift and their redshift distribution are
consistent with the star formation rate (SFR) over the entire range of
redshifts where the SFR has been measured with sufficient accuracy.
