Can life survive Gamma-Ray Bursts in the high-redshift universe?

TL;DR

This study assesses the potential for life to survive gamma-ray bursts in the high-redshift universe by analyzing GRB rates, galaxy properties, and the likelihood of benign environments over cosmic time.

Contribution

It provides a quantitative analysis of GRB rates in different galaxy types and redshifts, estimating the fraction of galaxies where life could survive despite high GRB activity.

Findings

Approximately 0.93 lethal GRBs affected Earth in the past 500 Myr.

The fraction of benign galaxies decreases from 50% at z~1.5 to 10% at z~3.

Milky Way-like galaxies dominate the benign galaxy population.

Abstract

Nearby Gamma-Ray Bursts (GRBs) have been proposed as a possible cause of mass extinctions on Earth. Due to the higher event rate of GRBs at higher redshifts, it has been speculated that life as we know it may not survive above a certain redshift (e.g. $z>0.5$). We examine the duty cycle of lethal (life-threatening) GRBs in the solar neighborhood, in the Sloan Digital Sky Survey (SDSS) galaxies and GRB host galaxies, with the dependence of the long GRB rate on star formation and metallicity properly taken into account. We find that the number of lethal GRBs attacking Earth within the past 500 Myr ($\sim$ epoch of the Ordovician mass extinction) is $0.93$. The number of lethal GRBs hitting a certain planet increases with redshift, thanks to the increasing star formation rate and decreasing metallicity in high-$z$ galaxies. Taking 1 per 500 Myr as a conservative duty cycle for life to survive, as evidenced by our existence, we find that there are still a good fraction of SDSS galaxies beyond $z=0.5$ where the GRB rate at half-mass radius is lower than this value. We derive the fraction of such benign galaxies as a function of redshift through Monte Carlo simulations, and find that the fraction is $\sim 50\%$ at $z\sim 1.5$ and $\sim 10\%$ even at $z \sim 3$. The mass distribution of benign galaxies is dominated by Milky-Way-like ones, thanks to their commonness, relatively large mass, and low star formation rate. GRB host galaxies are among the most dangerous ones.