Long GRBs are metallicity-biased tracers of star formation: evidence from host galaxies and redshift distribution
F. Y. Wang, Z. G. Dai (NJU)
TL;DR
This study shows that long gamma-ray bursts preferentially occur in low-metallicity, low-mass galaxies with high star formation rates, and that their redshift distribution aligns with star formation history when metallicity bias is considered.
Contribution
It provides evidence that long GRBs are biased tracers of star formation due to a low-metallicity cutoff of about 8.7 in metallicity, based on host galaxy mass and redshift distributions.
Findings
GRB host galaxies are low-metallicity, low-mass, high star formation rate.
A metallicity cutoff of 8.7 explains the GRB rate discrepancy.
Redshift distribution aligns with star formation history when metallicity bias is included.
Abstract
We investigate the mass distribution of long gamma-ray burst (GRB) host galaxies and the redshift distribution of long GRBs by considering that long GRBs occur in low-metallicity environments. We calculate the upper limit on the stellar mass of a galaxy which can produce long GRBs by utilizing the mass-metallicity (M-Z) relation of galaxies. After comparing with the observed GRB host galaxies masses, we find that the observed GRB host galaxy masses can fit the predicted masses well if GRBs occur in low-metallicity . GRB host galaxies have low metallicity, low mass, and high star formation rate compared with galaxies of seventh data release of the Sloan Digital Sky Survey. We also study the cumulative redshift distribution of the latest \emph{Swift} long GRBs by adding dark GRBs and 10 new GRBs redshifts from TOUGH survey. The observed discrepancy between…
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