JWST Medium Bands Reveal Missed Red Galaxies at z>5, Bridging LRDs and DSFGs While Exposing Gaps in High-z Luminosity Functions

The preprint by Withers et al. (arXiv:2606.06585, submitted June 2026) uses NIRCam medium-band imaging from the CANUCS, Technicolor, and JUMPS surveys to select emission-line galaxies at 4.9 ≲ z ≲ 8.9 via strong Hα and [OIII]+Hβ. From this they isolate 26 outliers termed REGs whose red continua coexist with extreme line strengths. These split into classic LRDs, extended dusty star-formers, and a compact population missed by standard LRD color cuts because of faint continua, line contamination, or flatter UV/optical slopes. The work is a preprint and has not undergone peer review; the sample of 26 objects remains modest and relies on photometric redshifts without full spectroscopic confirmation for every source. This population fills the previously empty parameter space between compact little red dots and extended DSFGs, implying that current z>5 luminosity functions undercount red, line-strong systems and that substantial dust production must already operate by 500 Myr after the Big Bang. Earlier JWST studies (Kocevski et al. 2024, ApJ; Labbe et al. 2023, arXiv:2306.07318) focused on color-selected LRDs and therefore systematically excluded the very objects now shown to be common, underestimating both number densities and the contribution of obscured star formation to cosmic reionization budgets.