Non-thermal Physics Drives Compact, Self-Regulated Galaxy Morphologies at Cosmic Dawn

JWST has revealed the first galaxies are unexpectedly bright and rapidly growing. Using synthetic observations of the Azahar cosmological simulation, we show that comprehensive non-thermal physics produces self-regulated galaxies matching z = 3–12 observations. This model explains bright z > 10 galaxies as compact starbursts in a broad brightness distribution. A model with standard hydrodynamics yields smaller concentrated systems, while calibrating supernova feedback produces unphysically large systems. Low-mass galaxies are smaller than JWST resolution but may be observable with future surveys.