Quiescent Low-mass Galaxies Observed by JWST in the Epoch of Reionization

[摘要] The surprising JWST discovery of a quiescent, low-mass ( M _⋆ = 10^8.7 M _⊙) galaxy at redshiftz= 7.3 (JADES-GS-z7-01-QU) represents a unique opportunity to study the imprint of feedback processes on early galaxy evolution. We build a sample of 130 low-mass ( M _⋆ ≲ 10^9.5 M _⊙) galaxies from theserracosmological zoom-in simulations, which show a feedback-regulated, bursty star formation history (SFH). The fraction of time spent in an active phase increases with the stellar mass fromf _duty ≈ 0.6 atM _⋆ ≈ 10^7.5 M _⊙ to ≈0.99 atM _⋆ ≥ 10⁹ M _⊙, and it is in agreement with the valuef _duty ≈ 0.75 estimated for JADES-GS-z7-01-QU. On average, 30% of the galaxies are quiescent in the range 6 ⋆ ≲ 10^8.3 M _⊙. However, none of these quiescent systems matches the spectral energy distribution of JADES-GS-z7-01-QU, unless their SFH is artificially truncated a few Myr after the main star formation peak. As supernova feedback can only act on a longer timescale (≳30 Myr), this implies that the observed abrupt quenching must be caused by a faster physical mechanism, such as radiation-driven winds from young massive stars and/or an active galactic nucleus.