2023ApJ...956...95B

We use JWST NIRCam observations of the massive lensing cluster field A2744 to develop a red galaxy selection of f_F444W > 1 μJy and f_F444W/f_F150W > 3.5 that picks out all nine >4.5σ Atacama Large Millimeter/submillimeter Array 1.1 or 1.2 mm sources and 17 of the 19 >5σ SCUBA-2 850 μm sources in the covered areas. We show that by using the red galaxies as priors, we can probe deeper in the SCUBA-2 850 μm image. This gives a sample of 44 >3σ SCUBA-2 850 μm sources with accurate positions, photometric redshifts, and magnifications. To investigate why our red galaxy selection picks out the 850 μm sources, we next analyze an extended sample of 167 sources with f_F444W > 0.05 μJy and f_F444W/f_F150W > 3.5. We find that the fainter f_F444W sources in this sample are too faint to be detected in the SCUBA-2 850 μm image. We also show that there is a strong drop between z < 4 and z > 4 (a factor of around 5) in the ratio of the far-infrared luminosity estimated from the 850 μm flux to the ν${L}_{\nu }^{d}$(5000) at rest-frame 5000 Å. We argue that this result may be due to the high-redshift sources having less dust content than the lower-redshift sources.