2026-09-24 アリゾナ大学
Artist’s visualization of an early galaxy and its surrounding gaseous environment. The orange structures represent metal-enriched gas being expelled from the galaxy, illustrating how young galaxies began dispersing heavy elements into their surroundings within the universe’s first 500 million years. The visualization is based on publicly available FIRE-2 cosmological simulation data and is not a direct telescope image. Yongda Zhu
＜関連情報＞
- https://news.arizona.edu/news/jwst-finds-early-galaxies-were-already-seeding-universe-heavy-elements
- https://www.nature.com/articles/s41550-026-02988-2
宇宙再電離の中間点以前の、金属に富んだ初期のバリオン循環 Early metal-enriched baryon cycling before the midpoint of cosmic reionization
Yongda Zhu, Zhiyuan Ji, George D. Becker, Jiani Ding, Eiichi Egami, Xiaohui Fan, Xiangyu Jin, Weizhe Liu, Jianwei Lyu, Zheng Ma, Suprabhas Narisetty, George H. Rieke, Yunjing Wu, Minghao Yue, Junyu Zhang & Marcia J. Rieke
Nature Astronomy Published:24 September 2026
DOI:https://doi.org/10.1038/s41550-026-02988-2
Abstract
Models predict that chemical enrichment and gas redistribution should begin rapidly once star formation starts, but direct constraints at the earliest epochs have been scarce. Here we show that metal-enriched gas in multiple ionic phases was already present around galaxies before the midpoint of cosmic reionization. Using JWST/NIRSpec rest-frame ultraviolet spectroscopy from SPURS, we detect blueshifted metal absorption in three galaxies at 7.2 < z < 9.3. The detected transitions span neutral, low-ionization and high-ionization species, including O I, Si II, C II, Si IV and C IV, with velocity offsets of ∣Δv∣ ≈ 50–250 km s−1 relative to nebular systemic redshifts. The ionic coexistence, overlapping velocity structure and equivalent-width ratios are consistent with outflowing or otherwise kinematically disturbed galaxy-associated gas, implying rapid metal enrichment. These results show that key conditions for baryon cycling were established in at least a subset of luminous galaxies within the first several hundred million years of cosmic time, well before the completion of reionization.
