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Accueil > Séminaires > Séminaires passés > Séminaires de 2009 > Do non-relativistic neutrinos consitute the Dark Matter

Theo M. Nieuwenhuizen

Do non-relativistic neutrinos consitute the Dark Matter

Lundi 25 mai 2009, à 16h

The Abell 1689 galaxy cluster is one of the best studied clusters. It is well relaxed, with an intruding subcluster in the North-East, which does not influence the South West hemisphere. Data for the total mass profile are available (from strong and weak lensing), for the galaxies (from light) and for the hot gas (X-rays).

In order to model this from first principles, it is assumed that the dark matter particles are WIMP fermions, and that the galaxies and gas are in hydrostatic equilibrium.

A good fit arises for a WIMP mass scale of a few eV, depending on its degeneracy g. The best choice seems g=12 : left and righthanded neutrinos in three families. Their mass is then about 1.45 eV, with 2% statistical uncertainty and a systematic uncertainty
from the Hubble constant. This approach automatically connects the 10 keV gas temperature to the one of alpha-particles.

Given a temperature of 0.045 K and a de Broglie length of 0.20 mm, the neutrinos establish a quantum structure of several million light years across, the largest known in the Universe.

The results are compatible with neutrino genesis, nucleosynthesis and free streaming. The neutrinos condense on the cluster at redshift z = 28, thereby causing reionization of the intracluster gas without assistance of heavy stars. The baryons are poor tracers of the dark matter density. These neutrinos constitute hot dark matter and conflict the
current cold dark matter paradigm.