A model to mini-quench early galaxies by balancing stellar feedback and gas accretion

The James Webb Space Telescope (JWST) has discovered a population of low-mass, early galaxies with very low levels of star formation over tens of Myr. These "mini-quenched" galaxies were one of the many surprises from JWST and still require a robust explanation. We seek to explain a few important properties of these galaxies, namely the timescales governing their star formation and quenching. We use a simple model that pairs stellar feedback with the forces binding gas to a z about 6 galaxy, and with plausible parameter choices, this model produces mini-quenching in galaxies approximately as large as observed mini-quenched galaxies -- up to total stellar masses of about 10 10 M. In our model, the ejected interstellar gas forms into a spherical shell that expands outward during quenching. Our novel improvement is allowing this expanding shell to prevent accreting gas from falling in, in contrast to other models whose shells do not interact with accreting gas. Using our model, if a galaxy accretes isotropically, we find that stellar feedback can reproduce observed timescales of mini-quenching with plausible galaxy-formation parameter values. However, at low halo masses, the quenching timescale of our model is too long (> 100 Myr). A potential solution for a long quenching time is for the galaxy to accrete via filaments, in which case only a portion of the shell interacts with the accreting gas and the quenching timescale decreases to more accepted values. However, the ram pressure from feedback cannot stop filaments with very small opening angles, as occur in some halo formation models, making mini-quenching impossible. Finally, we use this model to estimate the fraction of galaxies undergoing mini-quenching, finding that it can be large.