The first dusty galaxies across $6\lesssim z\lesssim 14$: Blue monsters, red monsters, and the bimodality of dust content in early galaxies

Abstract

JWST has revealed galaxies at $z>10$ with extremely blue UV-continuum slopes approaching ${\beta }_{\mathrm{UV}}\lesssim -2.4$, and low inferred dust contents. At similar redshifts, JWST and ALMA reveal dusty massive systems reaching ${\beta }_{\mathrm{UV}}\gtrsim -1$. We aim to explain blue monsters and red monsters at $z\gtrsim 10$ as different outcomes of supernova dust retention in clustered star-forming systems and connect this bimodality to dusty massive galaxies at $z\simeq 6$--7. We model dust removal in a cluster-dominated regime through cloud-scale mechanical blowout followed by breakout from stratified high-redshift disks. The shock-processed dust mass retained in the UV-attenuating layer is converted into a UV-continuum slope using absorption opacities derived from 3D hydrodynamical simulations of clustered supernovae in porous molecular clouds. In compact, gas-rich galaxies, efficient cloud blowout and disk breakout reduce the retained dust fraction to blue-monster levels, yielding ${\beta }_{\mathrm{UV}}\lesssim -2.4$. Larger stellar masses increase the retained dust column and produce red-monster-like systems with ${\beta }_{\mathrm{UV}}\gtrsim -1.5$, reaching ${\beta }_{\mathrm{UV}}\simeq -0.5$ when radiative losses weaken large-scale driving. The transition depends on whether clustered-supernova ejecta cross both the natal cloud and the galactic gas layer. Supernova dust production, shock processing, radiative losses, and mechanical venting can jointly explain UV-bright dust-poor galaxies and red dusty massive systems across $6\lesssim z\lesssim 14$.

4 pages, 1 figure. Accepted for publication as a Letter in Astronomy & Astrophysics