  Cold dark matter halos form within a smoothly distributed background of relic
neutrinos -- at least some of which are massive and non-relativistic at late
times. We calculate the accumulation of massive neutrinos around spherically
collapsing cold dark matter halos in a cosmological background. We identify the
physical extent of the "neutrino halo" in the spherical collapse model, which
is large in comparison with the virial radius of the dark matter, and
conditions under which neutrinos reaching the cold dark matter halo will remain
bound to the halo at late times. We calculate the total neutrino mass and bound
neutrino mass associated with isolated spherical halos for several neutrino
mass hierarchies and provide fitting formulae for these quantities in terms of
the cold dark matter halo mass and the masses of the individual neutrino
species.
