Mini-quenching of z = 4-8 galaxies by bursty star formation
Abstract
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⋆ = 107-109 M⊙ 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 per cent at z = 7 to ~2-4 per cent at z = 4, corresponding to comoving number densities of ~10-5 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 time-scale 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 time-scales 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.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2024
- DOI:
- 10.1093/mnras/stad3239
- arXiv:
- arXiv:2305.07066
- Bibcode:
- 2024MNRAS.527.2139D
- Keywords:
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- methods: numerical;
- galaxies: evolution;
- galaxies: formation;
- galaxies: high-redshift;
- galaxies: photometry;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 13 pages, 5 figures, 5 tables