# On the Cosmological Evolution of Long Gamma-ray Burst Properties

## TL;DR

This study investigates how long gamma-ray burst properties evolve with redshift, revealing correlations with cosmological implications and comparing their rate density to cosmic star formation history.

## Contribution

It provides new evidence for cosmological evolution of lGRB energies and durations, and estimates their rate density relative to star formation, considering selection effects.

## Key findings

- Isotropic energy correlates with redshift, indicating evolution.
- Jet opening angle correlates with redshift, but beaming-corrected energy does not.
- Intrinsic duration anti-correlates with redshift.

## Abstract

We examine the relationship between a number of long gamma-ray burst (lGRB) properties (isotropic emitted energy, luminosity, intrinsic duration, jet opening angle) and redshift. We find that even when accounting for conservative detector flux limits, there appears to be a significant correlation between isotropic equivalent energy and redshift, suggesting cosmological evolution of the lGRB progenitor. Analyzing a sub-sample of lGRBs with jet opening angle estimates, we find the beaming-corrected lGRB emitted energy does not correlate with redshift, but jet opening angle does. Additionally, we find a statistically significant anti-correlation between the intrinsic prompt duration and redshift, even when accounting for potential selection effects. We also find that - for a given redshift - isotropic energy is positively correlated with intrinsic prompt duration. None of these GRB properties appear to be correlated with galactic offset. From our selection-effect-corrected redshift distribution, we estimate a co-moving rate density for lGRBs, and compare this to the global cosmic star formation rate (SFR). We find the lGRB rate mildly exceeds the global star formation rate between a redshift of 3 and 5, and declines rapidly at redshifts above this (although we cannot constrain the lGRB rate above a redshift of about 6 due to sample incompleteness). We find the lGRB rate diverges significantly from the SFR at lower redshifts. We discuss both the correlations and lGRB rate density in terms of various lGRB progenitor models and their apparent preference for low-metallicity environments.