Do non-relativistic neutrinos constitute the dark matter?

The dark matter of the Abell 1689 Galaxy Cluster is modeled by thermal, non-relativistic gravitating fermions and its galaxies and X-ray gas by isothermal distributions. A fit yields a mass of h(70)(1/2) (12/(g) over bar)(1)/(4) 1.445(30) eV. A dark-matter fraction Omega(nu) = h(70)(-3/2) 0.1893(39) occurs for (g) over bar = 12 degrees of freedom, i.e., for 3 families of left-plus right-handed neutrinos with masses approximate to 2(3/4)G(F)(1/2)m(e)(2). Given a temperature of 0.045K and a de Broglie length of 0.20 mm, they establish a quantum structure of several million light years across, the largest known in the Universe. The virial alpha-particle temperature of 9.9 +/- 1.1keV/k(B) coincides with the average one of X-rays. The results are compatible with neutrino genesis, nucleosynthesis and free streaming. The neutrinos condense on the cluster at redshift z similar to 28, thereby causing reionization of the intracluster gas without assistance of heavy stars. The baryons are poor tracers of the dark-matter density.