The Cosmic History of Long Gamma-Ray Bursts

The cosmic formation rate of long gamma-ray bursts (LGRBs) encodes the evolution, across cosmic times, of the properties of their progenitors and of their environment. The LGRB formation rate and the luminosity function, with its redshift evolution, are derived by reproducing the largest sets of observations collected over the last four decades, namely the observer-frame prompt emission properties of the GRB samples detected by the Fermi and Compton Gamma Ray Observatory satellites and the redshift, luminosity, and energy distributions of the flux-limited, redshift-complete samples of GRBs detected by Swift. The model that best reproduces all these constraints consists of a GRB formation rate increasing with redshift proportional to(1 + z)(3.2), i.e., steeper than the star formation rate, up to z similar to 3, followed by a decrease proportional to(1 + z)(-3). On top of this, our model also predicts a moderate evolution of the characteristic luminosity function break proportional to(1 + z)(0.6). Models with only luminosity or rate evolution are excluded at >5 sigma significance. The cosmic rate evolution of LGRBs is interpreted as their preference for occurring in environments with metallicity 12+log(O/H) < 8.6, consistent with theoretical models and host galaxy observations. The LGRB rate at z = 0, accounting for their collimation, is rho(0) = 79(-33)(+57) Gpc(-3) yr(-1) (68% confidence interval). This corresponds to similar to 1% of broad-line Type Ibc supernovae producing a successful jet in the local universe. This fraction increases up to similar to 7% at z >= 3. Finally, we estimate that at least approximate to 0.2-0.7 yr(-1) of the Swift- and Fermi-detected bursts at z < 0.5 are jets observed slightly off-axis.

Automated summary

This study explores the cosmic formation rate and luminosity function evolution of long gamma-ray bursts (LGRBs) using observational data. The research reveals that the formation rate of LGRBs increases with redshift, peaking at around z=3, and then decreases. Additionally, the study finds that the characteristic luminosity function break of LGRBs evolves moderately with redshift. The overall findings are consistent with theoretical models and host galaxy observations.