初期の暗黒エネルギーが宇宙論の2大パズルを解決する可能性(Study: Early dark energy could resolve cosmology’s two biggest puzzles)

2024-09-13 マサチューセッツ工科大学(MIT)

＜関連情報＞

• https://news.mit.edu/2024/study-early-dark-energy-could-resolve-cosmologys-two-biggest-puzzles-0913
• https://academic.oup.com/mnras/article/533/4/3923/7750120

初期銀河と初期暗黒エネルギー：JWSTが明らかにしたハッブル張力と大質量明るい銀河のパズルの統一解 Early galaxies and early dark energy: a unified solution to the hubble tension and puzzles of massive bright galaxies revealed by JWST

Xuejian Shen, Mark Vogelsberger, Michael Boylan-Kolchin, Sandro Tacchella, Rohan P Naidu
Monthly Notices of the Royal Astronomical Society  Published:13 September 2024
DOI:https://doi.org/10.1093/mnras/stae1932

ABSTRACT

JWST has revealed a large population of UV-bright galaxies at z≳10 and possibly overly massive galaxies at z≳7⁠, challenging standard galaxy formation models in the ΛCDM cosmology. We use an empirical galaxy formation model to explore the potential of alleviating these tensions through an Early Dark Energy (EDE) model, originally proposed to solve the Hubble tension. Our benchmark model demonstrates excellent agreement with the UV luminosity functions (UVLFs) at 4≲z≲10 in both ΛCDM and EDE cosmologies. In the EDE cosmology, the UVLF measurements at z≃12 based on spectroscopically confirmed galaxies (eight galaxies at z≃11−13.5⁠) exhibit no tension with the benchmark model. Photometric constraints at 12≲z≲16 can be fully explained within EDE via either moderately increased star-formation efficiencies (⁠ϵ∗∼3−10 per cent at M_halo∼10^10.5M_⊙⁠) or enhanced UV variabilities (⁠σ_UV∼0.8−1.3 mag at M_halo∼10^10.5M_⊙⁠) that are within the scatter of hydrodynamical simulation predictions. A similar agreement is difficult to achieve in ΛCDM, especially at z≳14⁠, where the required σ_UV exceeds the maximum value seen in simulations. Furthermore, the implausibly large cosmic stellar mass densities inferred from some JWST observations are no longer in tension with cosmology when the EDE is considered. Our findings highlight EDE as an intriguing unified solution to a fundamental problem in cosmology and the recent tensions raised by JWST observations. Data at the highest redshifts reached by JWST will be crucial for differentiating modified galaxy formation physics from new cosmological physics.