Abstract
We use the BOSS DR9 quasar spectra to constrain non-thermal dark matter
models: cold-plus-warm dark matter and sterile neutrinos resonantly produced in
the presence of a lepton asymmetry. We establish constraints on the warm
thermal relic mass $m_x$ and its relative abundance
$F_wdm=Ømega_wdm/Ømega_dm$ using a suite of cosmological hydrodynamical
simulations in 28 C+WDM configurations. The 2D bounds in the $m_x - F_wdm$
parameter space approximately follow $F_wdm 0.243
(keV/m_x)^-1.31$. At 95% C.L., our limits from BOSS data alone imply
that $m_x> 2.5$ keV if $F_wdm>80\%$, while masses as low as 0.7 keV
are consistent with the data if $F_wdm<15\%$ of the total dark matter
density. We also constrain sterile neutrino mass and mixing angle by further
producing the non-linear flux power spectrum of 8 RPSN models, where the input
linear power spectrum is computed directly from the particles distribution
functions. We find values of lepton asymmetries for which sterile neutrinos as
light as 6 keV (resp. 3.5 keV) are consistent with BOSS at $2\sigma$ (resp.
$3\sigma$). These limits tighten by close to a factor of 2 for values of lepton
asymmetries departing from those yielding the coolest distribution functions.
Our bounds can be strengthened if we include higher-resolution data (XQ-100,
HIRES MIKE). At these scales, however, the flux power spectrum exhibits a
suppression compatible with the one expected from WDM. We do not investigate
the mechanism responsible for this suppression, but we show how much our bounds
would strengthen under the assumption that it is caused by the evolution of the
IGM temperature. A 7 keV neutrino produced in a lepton asymmetry $L =
|n_\nu_e - n_\nu_e|/s = 8 10^-6$ is consistent at
$1.9\sigma$ with BOSS data, and not necessarily excluded by our
higher-resolution bounds.
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