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 quiescent (QG) and post-starburst (PSB) galaxies using ultra-deep NIRCam and MIRI imaging from the JWST Advanced Deep Extragalactic Survey (JADES). Key to this is MIRI 7.7 mu m imaging which breaks the degeneracy between old stellar populations and dust attenuation at 3 &lt; z &lt; 6 by providing rest-frame J-band. Using this, we identify 23 passively evolving galaxies in UVJ color space in a mass-limited (log M-star/M-circle dot &gt;= 8.5) sample over 8.8 arcmin2. Evaluation of this selection with and without 7.7 mu m shows that dense wavelength coverage with NIRCam (8-11 bands including 1-4 medium-bands) can compensate for lacking the J-band anchor, meaning that robust selection of high-redshift QGs is possible with NIRCam alone. Our sample is characterized by rapid quenching timescales (similar to 100-600 Myr) with formation redshifts z(f )less than or similar to 8.5 and includes a potential record-holding massive QG at z(phot)=5.33(-0.17)(+0.16) and two QGs with evidence for significant residual dust content (A(V)similar to 1-2). In addition, we present a large sample of 12 log M-star/M-circle dot=8.5-9.5 PSBs, demonstrating that UVJ selection can be extended to low mass. 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 similar to 20 kpc. Moreover, the Cosmic Rose is part of a larger overdensity at z similar to 3.7 which contains 7/12 of our low-mass PSBs. Another 4 low-mass PSBs are members of an overdensity at z similar to 3.4; this result strongly indicates low-mass PSBs are preferentially associated with overdense environments at z&gt;3.