The recent reported discovery of a low-mass z=5.2 and an intermediate-mass z=7.3 quenched galaxy with JWST/NIRSpec is the first evidence of halted star formation above z≈5. Here we show how bursty star formation at z=4−8 gives rise to temporarily quenched, or mini-quenched galaxies in the mass range M⋆=107−109M⊙ using four models of galaxy formation: the periodic box simulation IllustrisTNG, the zoom-in simulations VELA and FirstLight and an empirical halo model. The main causes for mini-quenching are stellar feedback, lack of gas accretion onto galaxies and galaxy-galaxy interactions. The abundance of (mini-)quenched galaxies agrees across the models: the population first appears below z≈8, after which their proportion increases with cosmic time, from ∼0.5−1.0% at z=7 to ∼2−4% at z=4, corresponding to comoving number densities of ∼10−5 Mpc−3 and ∼10−3 Mpc−3, respectively. These numbers are consistent with star formation rate duty cycles inferred for VELA and FirstLight galaxies. Their star formation histories (SFHs) suggest that mini-quenching at z=4−8 is short-lived with a duration of ∼20−40 Myr, which is close to the free-fall timescale of the inner halo. However, mock spectral energy distributions of mini-quenched galaxies in IllustrisTNG and VELA do not match JADES-GS-z7-01-QU photometry, unless their SFHs are artificially altered to be more bursty on timescales of ∼40 Myr. Studying mini-quenched galaxies might aid in calibrating sub-grid models governing galaxy formation, as these may not generate sufficient burstiness at high redshift to explain the SFH inferred for JADES-GS-z7-01-QU.
@article{arxiv.2305.07066,
title = {Mini-quenching of $z=4-8$ galaxies by bursty star formation},
author = {Tibor Dome and Sandro Tacchella and Anastasia Fialkov and Daniel Ceverino and Avishai Dekel and Omri Ginzburg and Sharon Lapiner and Tobias J. Looser},
journal= {arXiv preprint arXiv:2305.07066},
year = {2023}
}