Core-Collapse Simulations Map Progenitor Structure to Neutron Star Masses, Reproducing Observed 1.35 Solar Mass Peak

The study uses a direct mapping between progenitor core compactness from existing 3D core-collapse simulations and the resulting neutron star gravitational mass. This produces a birth mass function that already incorporates fallback and accretion effects. Lower-mass neutron stars receive smaller natal kicks on average, while higher-mass ones receive larger kicks, further sculpting the distribution toward the observed shape.

The derived mass function accounts for the full observed range without additional tuning. Islands of black hole formation remove progenitors that would otherwise produce neutron stars above roughly 2 solar masses, naturally truncating the high-mass end. The resulting 21% black hole birth fraction emerges directly from the same simulation grid.

Prior analytic prescriptions for neutron star masses often required separate tuning for the low-mass peak and the high-mass tail. This work shows a single set of explosion physics plus kick-mass correlations suffices. Future gravitational-wave catalogs of merging compact objects can test the predicted joint mass-kick distribution within the next five years.

The main limitation is reliance on a limited set of 3D progenitors; expanding the grid to lower-metallicity and higher-mass stars would tighten the predicted black hole fraction.