Speaker
Description
We reconsider the problem of determining the warmness of dark matter
from the growth of large scale structures. In particular, we have
re-analyzed the previous work of Viel et al 2013, based on high
resolution Lyman-alpha forest spectra. In fact, the flux power
spectrum exhibits a cut-off below ~ 1.5 Mpc/h, this may be explained
by the temperature of the intergalactic medium (IGM) or be due to the
free-streaming of dark matter particles. We show that if the IGM
temperature at high redshifts was low enough (rising at later times)
then the data indeed prefer warm dark matter. Assuming this broader
range of thermal histories, we find that mWDM >= 2.1 keV for thermal
relic at 95% CL (mNRP >= 12 keV for non-resonantly produced sterile
neutrino). We discuss an independent method that would allow to
exclude the influence of WDM on observable small-scale structures, or
would lead to the discovery of WDM. We also determine values of
lepton asymmetry making resonantly produced 7 keV sterile neutrinos
consistent with the data.
