2023-07-05 オークリッジ国立研究所(ORNL)
◆研究結果は、従来のモデルとは異なり、ウォームダークマターの存在を示唆しています。この研究は、ダークマターに関する長い間の仮定を揺るがすだけでなく、コンピュータ上での計算の困難さでも注目されています。
＜関連情報＞
- https://www.ornl.gov/news/california-researchers-use-ornl-supercomputer-summit-investigate-mystery-cosmos-dark-matter
- https://journals.aps.org/prd/abstract/10.1103/PhysRevD.108.023502
ライマンαフォレストのパワースペクトルから、暖かい暗黒物質に対する新たな制約を発見 New constraints on warm dark matter from the Lyman-α forest power spectrum
Bruno Villasenor, Brant Robertson, Piero Madau, and Evan Schneider
Physics Review D Published 5 July 2023
DOI:https://doi.org/10.1103/PhysRevD.108.023502
ABSTRACT
The forest of Lyman-α absorption lines detected in the spectra of distant quasars encodes information on the nature and properties of dark matter and the thermodynamics of diffuse baryonic material. Its main observable—the 1D flux power spectrum (FPS)—should exhibit a suppression on small scales and an enhancement on large scales in warm dark matter (WDM) cosmologies compared to standard ΛCDM. Here, we present an unprecedented suite of 1080 high-resolution cosmological hydrodynamical simulations run with the graphics processing unit-accelerated code cholla to study the evolution of the Lyman-α forest under a wide range of physically motivated gas thermal histories along with different free-streaming lengths of WDM thermal relics in the early Universe. A statistical comparison of synthetic data with the forest FPS measured down to the smallest velocity scales ever probed at redshifts 4.0≲z≲5.2 [E. Boera et al., Revealing reionization with the thermal history of the intergalactic medium: New constraints from the Lyα flux power spectrum, Astrophys. J. 872, 101 (2019)] yields a lower-limit mWDM>3.1 keV (95% C.L.) for the WDM particle mass and constrains the amplitude and spectrum of the photoheating and photoionizing background produced by star-forming galaxies and active galactic nuclei at these redshifts. Interestingly, our Bayesian inference analysis appears to weakly favor WDM models with a peak likelihood value at the thermal relic mass of mWDM=4.5 keV. We find that the suppression of the FPS from free-streaming saturates at k≳0.1 s km−1 because of peculiar velocity smearing, and this saturated suppression combined with a slightly lower gas temperature provides a moderately better fit to the observed small-scale FPS for WDM cosmologies.
