  Recently, to explain the origin of neutrino masses a model based on confining
some hidden fermionic bound states into right-handed chiral neutrinos has been
proposed. One of the consequences of condensing the hidden sector fields in
this model is the presence of sterile composite Dirac neutrinos of keV mass,
which can form viable warm dark matter particles. We have analyzed constraints
on this model from the observations of satellite based telescopes to detect the
sterile neutrinos in clusters of galaxies.
