A Redshift-based Red Selection of Dusty Star-forming Galaxies

Abstract We use JWST observations (1.5–4.44 μ m), together with complete Atacama Large Millimeter/submillimeter Array (ALMA) observations (870 μ m and/or 1.2 mm), of the massive lensing cluster field A2744 to show that galaxies between z = 1.5 and z = 5.5 with rest-frame red colors f J / f V > 3 correspond to dusty star-forming galaxies (DSFGs), little red dots (LRDs), and quiescent galaxies. The color selection picks out 34 of the 41 >4.5 σ ALMA sources in the field (83%). We find that the luminous (rest-frame L ν (1.22 μ m) > 3.6 × 10 29 erg s −1 Hz −1 ) red sources are generally extended, while the less luminous red sources are almost all compact and correspond to the LRD population. We also find that the great majority of the luminous, extended red sources are DSFGs based on the ALMA data, with a small admixture of quiescent galaxies at z ≲ 3–4 that we identify based on their location in the rest-frame U − V versus V − J diagram. We do not detect any LRDs or quiescent galaxies at the >3 σ level in the ALMA images. Roughly 10% of the DSFGs have high rest-frame X-ray luminosities (here L (8–28 keV) > 2.5 × 10 43 erg s −1 ) and must be dominated by active galactic nuclei. The DSFGs and quiescent galaxies nearly all have M * > 10 10 M ⊙ . These massive galaxies become rare at z > 5, paralleling the falloff in the number of detected DSFGs.