Hunting Thermal Relics in the DESI DR1 Lyα Forest
Abstract
We investigate constraints on additional relativistic species and thermal sterile neutrinos using the DESI DR1 one-dimensional Lyman-α forest power spectrum, combined with Planck 2018 CMB and DESI DR2 BAO measurements. We consider both the ΛCDM+Neff extension and a thermal with a different-temperature sterile-neutrino (DTS) scenario, in which the sterile relic can be colder than the standard neutrino background. We first validate the DESI two-parameter P1D compression for the DTS model, finding that the residual cosmological dependence not captured by the compressed parameters remains below 0.15%. No significant evidence for additional radiation or a sterile component is found. For ΛCDM+Neff, we obtain Neff<3.41 at 95% credibility from CMB+DESI-BAO+DESI-P1D. In the DTS scenario, the full CMB+DESI-BAO+DESI-P1D combination yields the stringent bound mseff<0.061 eV, highlighting the complementarity of BAO and Lyman-α information in constraining the massive sterile abundance. We further interpret the allowed ΔNeff in terms of thermal light relics, deriving lower limits on their decoupling temperatures that reach the QCD epoch.
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BibTeX
@misc{silva2026hunting,
title = {{Hunting Thermal Relics in the DESI DR1 Ly$α$ Forest}},
author = {Emanuelly Silva and Artur Ladeira and Rafael C. Nunes and Eleonora Di Valentino},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22581},
eprint = {2609.22581},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22581},
}
RIS
TY - UNPB
TI - Hunting Thermal Relics in the DESI DR1 Lyα Forest
AU - Emanuelly Silva
AU - Artur Ladeira
AU - Rafael C. Nunes
AU - Eleonora Di Valentino
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22581
UR - https://arxiv.org/abs/2609.22581
AB - We investigate constraints on additional relativistic species and thermal sterile neutrinos using the DESI DR1 one-dimensional Lyman-α forest power spectrum, combined with Planck 2018 CMB and DESI DR2 BAO measurements. We consider both the ΛCDM+N_eff extension and a thermal with a different-temperature sterile-neutrino (DTS) scenario, in which the sterile relic can be colder than the standard neutrino background. We first validate the DESI two-parameter P_1D compression for the DTS model, finding that the residual cosmological dependence not captured by the compressed parameters remains below 0.15%. No significant evidence for additional radiation or a sterile component is found. For ΛCDM+N_eff, we obtain N_eff<3.41 at 95% credibility from CMB+DESI-BAO+DESI-P_1D. In the DTS scenario, the full CMB+DESI-BAO+DESI-P_1D combination yields the stringent bound m_s^eff<0.061 eV, highlighting the complementarity of BAO and Lyman-α information in constraining the massive sterile abundance. We further interpret the allowed ΔN_eff in terms of thermal light relics, deriving lower limits on their decoupling temperatures that reach the QCD epoch.
ER -