Gamma-ray Burst Jets: Evolution Over Cosmic Time And New Predictions For The High Redshift Star Formation Rate

There is tantalizing evidence that the jets launched from gamma-ray bursts (GRBs) are narrower (more tightly collimated) at higher redshifts. This has important implications on both the physics of the jet launch, and also on estimates of the high redshift star formation rate from gamma-ray bursts. We present the observational evidence for the GRB jet opening angle-redshift anti-correlation, discuss the potential physical mechanisms responsible for this correlation, and, finally, provide estimates of the high redshift star formation rate accounting for this effect.