2023-10-03 ノースウェスタン大学
◆この研究は、宇宙の誕生後の初期の銀河の形成過程を詳細なコンピューターシミュレーションで調査し、星の爆発的な形成が明らかになりました。これにより、宇宙の初期の銀河が質量よりも明るさに影響を受けることが示され、標準宇宙モデルと調和する新たな理解が得られました。この研究は、ジェームズ・ウェッブ宇宙望遠鏡の観測データを活用し、初期の宇宙の形成過程に新たな光を当てました。
＜関連情報＞
- https://news.northwestern.edu/stories/2023/09/bursts-of-star-formation-explain-mysterious-brightness-at-cosmic-dawn/
- https://iopscience.iop.org/article/10.3847/2041-8213/acf85a
宇宙夜明けの明るい銀河の多さは、バースト的な星形成で自然に説明できる Bursty Star Formation Naturally Explains the Abundance of Bright Galaxies at Cosmic Dawn
Guochao Sun, Claude-André Faucher-Giguère, Christopher C. Hayward, Xuejian Shen, Andrew Wetzel, and Rachel K. Cochrane
The Astrophysical Journal Letters Published 2023 October 3
DOI:10.3847/2041-8213/acf85a
Abstract
Recent discoveries of a significant population of bright galaxies at cosmic dawn have enabled critical tests of cosmological galaxy formation models. In particular, the bright end of the galaxys’ UV luminosity functions (UVLFs) appear higher than predicted by many models. Using approximately 25,000 galaxy snapshots at 8 ≤ z ≤ 12 in a suite of FIRE-2 cosmological “zoom-in” simulations from the Feedback in Realistic Environments (FIRE) project, we show that the observed abundance of UV-bright galaxies at cosmic dawn is reproduced in these simulations with a multichannel implementation of standard stellar feedback processes, without any fine-tuning. Notably, we find no need to invoke previously suggested modifications, such as a nonstandard cosmology, a top-heavy stellar initial mass function, or a strongly enhanced star formation efficiency. We contrast the UVLFs predicted by bursty star formation in these original simulations to those derived from star formation histories (SFHs) smoothed over prescribed timescales (e.g., 100 Myr). The comparison demonstrates that the strongly time-variable SFHs predicted by the FIRE simulations play a key role in correctly reproducing the observed, bright-end UVLFs at cosmic dawn: the bursty SFHs induce order-or-magnitude changes in the abundance of UV-bright (MUV ≲ −20) galaxies at z ≳ 10. The predicted bright-end UVLFs are consistent with both the spectroscopically confirmed population and the photometrically selected candidates. We also find good agreement between the predicted and observationally inferred integrated UV luminosity densities, which evolve more weakly with redshift in FIRE than suggested by some other models.
