Moderate Lyman-Werner Flux Produces 10^5 Solar Mass Seeds in Common Halos

The 65 cosmological zoom-in runs span assembly rates from 0.01 to 7 solar masses per year and J21 values from below 1 to above 10. A new radial-infall estimator calibrated against sink-particle literature reproduces final stellar masses to within a factor of two. The key transition occurs between J21 of 1 and 10; halos above this threshold maintain the high accretion needed for supermassive stars while halo dynamical time shows no statistically significant correlation with outcome.

This result relaxes the extreme ultraviolet background requirement of classical direct-collapse models. Semi-analytic volume estimates indicate that intermediate J21 regimes are far more common, implying heavy seeds could form in typical rather than rare atomic-cooling halos. The finding connects to JWST reports of overmassive black holes at z greater than 6 by supplying a pathway that does not demand synchronized halo mergers or pristine metal-free gas at all times.

The main limitation is the absence of explicit protostellar feedback and magnetic fields that could reduce final masses. Follow-up simulations that couple radiation hydrodynamics with sink particles across the full J21 range would tighten the mass function and test whether the inflow threshold remains robust once feedback is included.