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

Bruce Hoeneisen
2022 International Journal of Astronomy and Astrophysics International Journal of Astronomy and Astrophysics  
The root-mean-square of non-relativistic warm dark matter particle velocities scales as ( ) ( ) , where a is the expansion parameter of the universe. This velocity dispersion results in a cut-off of the power spectrum of density fluctuations due to dark matter free-streaming. Let ( ) fs eq k t be the free-streaming comoving cut-off wavenumber at the time of equal densities of radiation and matter. We obtain ( ) 0.14 rms 0.12 ( ) 1 fs eq 1.5 Mpc k t − > . These results are in agreement with
more » ... ous measurements based on spiral galaxy rotation curves, and on the formation of first galaxies and reionization. These measured parameters determine the temperature-to-mass ratio of warm dark matter. This ratio happens to be in agreement with the no freeze-in and no freeze-out warm dark matter scenario of spin 0 dark matter particles decoupling early on from the standard model sector. Spin 1/2 and spin 1 dark matter are disfavored if nature has chosen the no freeze-in and no freeze-out scenario. An extension of the standard model of quarks and leptons, with scalar dark matter that couples to the Higgs boson that is in agreement with all current measurements, is briefly reviewed. Discrepancies with limits on dark matter particle mass that can be found in the literature are addressed.
doi:10.4236/ijaa.2022.123015 fatcat:2gqre6cjbre3lhvvozwvkwipza