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

Abstract

The surprising JWST discovery of a quiescent, low-mass (M ⋆ = 108.7 M ⊙) galaxy at redshift z = 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 ⋆ ≲ 109.5 M ⊙) galaxies from the serra cosmological 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 from f duty ≈ 0.6 at M ⋆ ≈ 107.5 M ⊙ to ≈0.99 at M ⋆ ≥ 109 M ⊙, and it is in agreement with the value f duty ≈ 0.75 estimated for JADES-GS-z7-01-QU. On average, 30% of the galaxies are quiescent in the range 6 < z < 8.4; they become the dominant population at M ⋆ ≲ 108.3 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.

Can Supernovae Quench Star Formation in High-z Galaxies?

“…However, in Gelli et al (2023), we showed that: (i) in order to reproduce the observed spectra of JADES-GS-z7-01-QU, an abrupt quenching of the simulated low-mass galaxy is required; and (ii) SNe alone cannot induce such an abrupt SF quenching in the low-mass galaxies identified in our cosmological simulations (Pallottini et al 2022). The same results have been later confirmed by Dome et al (2024) using the Illustris TNG, VELA, and FirstLight simulations.…”

“…This finding lends further support to the previous studies based on cosmological simulations and quenching timescales reaching the same conclusion. In fact, not only does the quenching appear to be too swift to be produced by SNe (Gelli et al 2023;Dome et al 2024), but our model also convincingly shows that the SFR level sustained in the observed burst cannot produce enough energy to suppress SF.…”

“…Note that such a kind of top-hat SFH is often assumed in spectral energy distribution (SED) fitting models (e.g., BAGPIPES; Carnall et al 2018) successfully reproducing the observed galaxies' properties. This top-hat approximation allows us to obtain a good estimate of the typical timescales required for a burst to produce the total quenching, although in a more realistic scenario the action of SN feedback will cause a gradual decline of the SFR prior to the quenching (e.g., see Gelli et al 2023). With this ansatz, the final stellar mass is then given by M å = SFR × Δt b .…”

Two Distinct Classes of Quiescent Galaxies at Cosmic Noon Revealed by JWST PRIMER and UNCOVER

“…The choice of feedback model has also been shown to impact the overall size-mass relation at low masses (e.g., Pillepich et al 2018), with the caveat that the sample is not separated into star-forming and quiescent populations. At higher redshifts, supernovae have been proposed as potential drivers of low-mass galaxy quenching, though they have been shown to not impart sufficient energy to halt star formation in the Looser et al (2024) or Strait et al (2023) high-redshift mini-quenched galaxy candidates (Gelli et al 2024(Gelli et al , 2023. Quenching via environmental interactions would result in minimal structural changes to the stellar light of low-mass galaxies, while stellar feedback quenching makes galaxies larger (Übler et al 2014).…”

Rapid Chemical Enrichment by Intermittent Star Formation in GN-z11

“…Hence, the dust produced by massive stars associated with the observed stellar population must have been efficiently evacuated (or destroyed) along with most of the gas by powerful galactic outflows driven by the radiation pressure produced by their compact (;100 pc), young (20-30 Myr) stellar component (Ferrara et al 2023;Fiore et al 2023;Ziparo et al 2023). Such feedback temporarily quenches star formation (Gelli et al 2023;Looser et al 2023) until the gas content of the galaxy is restored by efficient cosmological gas accretion, entailing a duty cycle of ;50-100 Myr.…”