Measurement of the Dark Matter Velocity Dispersion with Galaxy Stellar Masses, UV Luminosities, and Reionization

The root-mean-square of non-relativistic warm dark matter particle velocities scales as vhrms(a)=vhrms(1)/a , where a is the expansion parameter universe. This velocity dispersion results in cut-off power spectrum density fluctuations due to free-streaming. Let kfs (teq) be free-streaming comoving wavenumber at time equal densities radiation and matter. We obtain 68% confidence, from observed distributions galaxy stellar masses rest frame ultra-violet luminosities. result consistent with reionization. From mass we limits vhrms(1)kfs >1.5 Mpc-1. These are agreement previous measurements based on spiral rotation curves, formation first galaxies measured parameters determine temperature-to-mass ratio happens no freeze-in freeze-out scenario spin 0 particles decoupling early standard model sector. Spin 1/2 1 disfavored if nature has chosen scenario. An extension quarks leptons, scalar that couples Higgs boson all current measurements, briefly reviewed. Discrepancies can found literature addressed.