Tightening Bounds on Warm Dark Matter with High-Redshift Gamma-Ray Bursts
Abstract
The cold dark matter paradigm successfully explains large-scale structure but faces persistent tensions on small scales. Warm dark matter (WDM) with keV-scale particles can alleviate these issues by suppressing small-scale structure formation. The presence of collapsed structures at high redshifts places strong lower limits on the WDM particle mass mx. Gamma-ray bursts (GRBs) are ideal high-redshift probes due to their extreme brightness. Using the most recent \emph{Swift} GRB data accumulated over the past two decades, we derive robust constraints on mx by conservatively assuming that the comoving GRB formation rate is proportional to the cosmic star formation rate (SFR), with an additional redshift evolution parameterized as (1+z)α. Applying a maximum-likelihood analysis to 118 GRBs with redshift z<10 and luminosity L≥ 4.0×1052 erg s−1, we obtain mx ≳ 1.23 keV and α=1.57+1.14−0.57 at the 95\% confidence level (CL). The no-evolution scenario (α=0), in which the GRB rate exactly traces the SFR without additional redshift evolution, is excluded at the 5σ level. Adopting the best-fit value α=1.57 as a prior tightens the lower limit on mx to mx ≳ 1.59 keV at the 95\% CL. These robust constraints demonstrate that GRBs are a powerful probe of the early Universe. A better understanding of the relationship between the GRB rate and the SFR would enable even tighter limits on WDM models.
Versions
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BibTeX
@misc{wei2026tightening,
title = {{Tightening Bounds on Warm Dark Matter with High-Redshift Gamma-Ray Bursts}},
author = {Jun-Jie Wei and Jing-Meng Hao and Ding-Fang Hu and Yang Liu and Bao Wang and Xi Kang and Xue-Feng Wu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.25261},
eprint = {2607.25261},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.25261},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Tightening Bounds on Warm Dark Matter with High-Redshift Gamma-Ray Bursts
AU - Jun-Jie Wei
AU - Jing-Meng Hao
AU - Ding-Fang Hu
AU - Yang Liu
AU - Bao Wang
AU - Xi Kang
AU - Xue-Feng Wu
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2607.25261
UR - https://arxiv.org/abs/2607.25261
AB - The cold dark matter paradigm successfully explains large-scale structure but faces persistent tensions on small scales. Warm dark matter (WDM) with keV-scale particles can alleviate these issues by suppressing small-scale structure formation. The presence of collapsed structures at high redshifts places strong lower limits on the WDM particle mass m_x. Gamma-ray bursts (GRBs) are ideal high-redshift probes due to their extreme brightness. Using the most recent \emph{Swift} GRB data accumulated over the past two decades, we derive robust constraints on m_x by conservatively assuming that the comoving GRB formation rate is proportional to the cosmic star formation rate (SFR), with an additional redshift evolution parameterized as (1+z)^α. Applying a maximum-likelihood analysis to 118 GRBs with redshift z<10 and luminosity L≥ 4.0×10^52 erg s^−1, we obtain m_x ≳ 1.23 keV and α=1.57^+1.14_−0.57 at the 95\% confidence level (CL). The no-evolution scenario (α=0), in which the GRB rate exactly traces the SFR without additional redshift evolution, is excluded at the 5σ level. Adopting the best-fit value α=1.57 as a prior tightens the lower limit on m_x to m_x ≳ 1.59 keV at the 95\% CL. These robust constraints demonstrate that GRBs are a powerful probe of the early Universe. A better understanding of the relationship between the GRB rate and the SFR would enable even tighter limits on WDM models.
ER -