Unveiling Dark Matter free-streaming at the smallest scales with high redshift Lyman-alpha forest
arXiv (Cornell University)(2023)
摘要
This study introduces novel constraints on the free-streaming of thermal
relic warm dark matter (WDM) from Lyman-α forest flux power spectra. Our
analysis utilises a high-resolution, high-redshift sample of quasar spectra
observed using the HIRES and UVES spectrographs (z=4.2-5.0). We employ a
Bayesian inference framework and a simulation-based likelihood that encompasses
various parameters including the free-streaming of dark matter, cosmological
parameters, the thermal history of the intergalactic medium, and inhomogeneous
reionization, to establish lower limits on the mass of a thermal relic WDM
particle of 5.7 keV (at 95% C.L.). This result surpasses previous
limits from the Lyman-α forest through reduction of the measured
uncertainties due to a larger statistical sample and by measuring clustering to
smaller scales (k_ max=0.2 km^-1 s). The approximately
two-fold improvement due to the expanded statistical sample suggests that the
effectiveness of Lyman-α forest constraints on WDM models at high
redshifts are limited by the availability of high-quality quasar spectra.
Restricting the analysis to comparable scales and thermal history priors as in
prior studies (k_ max<0.1 km^-1 s) lowers the bound on the
WDM mass to 4.1 keV. As the precision of the measurements
increases, it becomes crucial to examine the instrumental and modelling
systematics. On the modelling front, we argue that the impact of the thermal
history uncertainty on the WDM particle mass constraint has diminished due to
improved independent observations. At the smallest scales, the primary source
of modeling systematic arises from the structure in the peculiar velocity of
the intergalactic medium and inhomogeneous reionization.
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关键词
dark matter,smallest scales,forest,free-streaming,lyman-alpha
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