To High Redshift and Low Mass: Exploring the Emergence of Quenched Galaxies and Their Environments at 3 < z < 6 in the Ultra-deep JADES MIRI F770W Parallel

We present the robust selection of high-redshift quiescent galaxies (QG) and poststarburst (PSB) galaxies using ultra-deep NIRCam and MIRI imaging from the JWST Advanced Deep Extragalactic Survey (JADES). At $3 < z < 6$ , MIRI $7.7\ \mu\mathrm{m}$ imaging provides rest-frame $J$ band, which is commonly used to break the degeneracy between old stellar populations and dust attenuation at lower redshifts. We identify $23$ passively evolving galaxies in UVJ color space in a mass-limited ($\mathrm{log}_{10}(M_{\ast}/M_{\odot}) \geq 8.5$ ) sample over $8.8\ \mathrm{arcmin}^{2}$ . An evaluation of the contribution of the $7.7\ \mu\mathrm{m}$ shows that JADES-like NIRCam coverage ($9+$ photometric bands) can compensate for lacking the $J$ band at these redshifts; however, more limited three-band selections perform better with MIRI. Our sample is characterized by rapid quenching timescales ($\sim 100-600\ \mathrm{Myr}$ ) with formation redshifts $z_{\mathrm{form}} \leq 9$ and includes a potential record-holding massive QG at and two QGs with evidence for significant residual dust content ($A_{V} \sim 1-2$ ). In addition, we present a large sample of $12$ $\mathrm{log}_{10}(M_{\ast}/M_{\odot}) = 8.5-9.5$ PSBs, demonstrating that UVJ selection can be extended to low mass. An analysis of the environment of our sample reveals that the group known as the Cosmic Rose contains a massive QG and a dust-obscured star-forming galaxy (a so-called Jekyll and Hyde pair) plus three additional QGs within $\sim 20\ \mathrm{kpc}$ . Moreover, the Cosmic Rose is part of a larger overdensity at $z \sim 3.7$ , which contains $7/12$ of our low-mass PSBs. Another four low-mass PSBs are members of an overdensity at $z \sim 3.4$ ; this result strongly indicates low-mass PSBs are preferentially associated with overdense environments at $z > 3$ .

The Astrophysical Journal, Volume 975, Issue 1, id.85, 25 pages