Born in the Dark: The Catastrophic Collapse of Fuzzy Dark Matter Solitons as the Origin of Little Red Dots

Abstract JWST surveys have uncovered a population of compact, red sources (“Little Red Dots,” LRDs) at z ≥ 5 that exhibit broad Balmer emission yet remain X-ray faint, implying heavy obscuration with N H ≥ 10 24 cm −2 . We propose that LRDs trace a short-lived, obscured phase associated with rapid baryonic inflow inside the deep solitonic cores of fuzzy dark matter halos. Combining the soliton size scaling with the observed compact radii ( r e ∼ 30–100 pc), we find that while a particle mass of m ∼ 2 × 10 −22 eV provides a direct match for mature systems, the observed size–mass relation is fully consistent with heavier bosons ( m 22 ≳ 20, satisfying Ly α constraints) if LRDs represent a progenitor phase where the central black hole is still growing ( M BH < M c ). We adopt m 22 = 2 as a fiducial baseline to demonstrate the thermodynamic instability. A conservative mass-budget estimate indicates that configurations reaching N H ≥ 10 24 –10 25 cm −2 require densities for which radiative losses (cooling and/or diffusion) occur faster than the dynamical time, suggesting that a long-lived static hot atmosphere is unlikely (an “Opacity Crisis”) and that rapid inflow or radiation-pressure-driven evolution is favored. Using 512 3 pseudospectral Schrödinger–Poisson simulations of idealized soliton mergers, we illustrate that compact, high-density soliton cores form robustly under representative scalings. We discuss observational implications and tests and outline the need for future radiation-hydrodynamic modeling to predict demographics and detailed spectra.