The New Dark Matter Density Profile from JWST JADES Galaxies

Abstract

We present the first dark matter density profile derived directly from James Webb Space Telescope JADES Data Release~3 NIRSpec observations of $N = 587$ galaxies spanning the cosmic noon epoch $1.5 \leq z \leq 3.5$. From each NIRSpec G235M/G395M spectrum we extract the H$\alpha$ emission-line velocity dispersion $\sigma_{\rm ha}$, stack galaxies in four redshift bins of $\Delta z = 0.5$, and reconstruct representative group rotation curves within the General Theory of Relativity. Fitting the four-parameter modified exponential model and deriving the exact GTR energy density, we reduce the profile to a compact $[2/3]$ Pad\'{e} approximant with all coefficients determined in closed form from JWST observations. The profile is cusp-free, fully analytic, and redshift-dependent. Energy conditions, causality, and orbital stability are all satisfied. Most strikingly, the central density $\rho(0)$ varies by less than $15\%$ across $z = 1.5$--$3.5$ despite a $35\%$ decline in the asymptotic rotation velocity, revealing a universal dark matter core saturation density at cosmic noon decoupled from baryonic evolution.