Sterile Neutrinos

[Blob]

Hum,
Dark matter could be made of sterile neutrinos, a low-mass particle that does not participate in the weak interaction, but which could be created through flavour oscillation. They would still interact via gravity.

Relic keV sterile neutrinos and reionisation
Authors: Peter L. Biermann, Alexander Kusenko

A sterile neutrino with mass of several keV can account for cosmological dark matter, as well as explain the observed velocities of pulsars. We show that X-rays produced by the decays of these relic sterile neutrinos can boost the production of molecular hydrogen, which can speed up the cooling of gas and the early star formation, which can, in turn, lead to a reionisation of the universe at a high enough redshift to be consistent with the WMAP results.

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[antoniseb]

If they are a significant fraction of Cold Dark Matter, the crucial thing about them is that we need to show a mechanism by which they have energies which make them energetic enough to mostly not be bound to stars or planets, but not so energetic to escape galaxies and clusters.

[ngc3314]

If they are a significant fraction of Cold Dark Matter, the crucial thing about them is that we need to show a mechanism by which they have energies which make them energetic enough to mostly not be bound to stars or planets, but not so energetic to escape galaxies and clusters.

Biermann spends a good bit of time here lately, so we got the long version. Indeed, the key thing to making this at all plausible is that there is a relevant energy range which is not ruled out by either the cosmological argument (that is, they can have the right energy to be CDM and not HDM - masses of some keV). A cool (or at least intellectually seductive) thing about this particular model is that they can form degenerate configurations in the early Universe (behavior generic to massive neutrinos) which could be eaten very quickly if even a stellar-mass seed black hole forms in one of them (allowing this whole neutrino configuration to form very massive black holes really fast on cosmic time scales without affecting any nucleosynthesis density measurements). We were a very tough crowd for his contention that the most productive thing that Chandra and XMM-Newton could do now is devote the next five years to building up enough statistics to look for the X-ray decay lines of these things from the density peaks of galaxy clusters. Still, somebody did look into coadding all the galaxy-cluster X-ray spectra in the archive to see whether that would give a helpful limit (let alone detection).