JWST PRIMER: strong evidence for the environmental quenching of low-mass galaxies out to $\text{z}\simeq 2$

Abstract

We present the results of a study investigating the galaxy stellar-mass function (GSMF), size-mass relations and morphological properties of star-forming and quiescent galaxies over the redshift range $0.25<z<2.25$, using the JWST PRIMER survey. The depth of the PRIMER near-IR imaging allows us to confirm the double Schechter function shape of the quiescent GSMF out to $z\simeq 2.0$, via a clear detection of the upturn at ${\log }_{10}(M_{\star }/M_{\odot })\le 10$ thought to be induced by environmental quenching. In addition to the GSMF, we confirm that quiescent galaxies can be split into separate populations at ${\log }_{10}(M_{\star }/M_{\odot })\simeq 10$, based on their size-mass relations and morphologies. We find that low-mass quiescent galaxies have more disk-like morphologies (based on Sérsic index, Gini coefficient and $M_{20}$ metrics) and follow a shallower size-mass relation than their high-mass counterparts. Indeed, the slope of the size-mass relation followed by low-mass quiescent galaxies is indistinguishable from that followed by star-forming galaxies, albeit with a lower normalization. Moreover, within the errors, the evolution in the median size of low-mass quiescent galaxies is indistinguishable from that followed by star-forming galaxies ($R_e\propto (1+z{)}^{-0.25\pm 0.03})$, and significantly less rapid than that displayed by high-mass quiescent galaxies ($R_e\propto (1+z{)}^{-1.14\pm 0.03})$. Overall, our results are consistent with low and high-mass quiescent galaxies following different quenching pathways. The evolution of low-mass quiescent galaxies is qualitatively consistent with the expectations of external/environmental quenching (e.g. ram-pressure stripping). In contrast, the evolution of high-mass quiescent galaxies is consistent with internal/mass quenching (e.g. AGN feedback) followed by size growth driven by minor mergers.

14 pages, 5 figures. Submitted to MNRAS. Comments welcome!