ar X iv : a st ro - p h / 95 04 01 4 v 1 5 A pr 1 99 5 CITA - 95 - 9 A Warm - Plus - Hot Dark Matter

We investigate a new hybrid-model universe containing two types of dark matter, one " warm " and the other " hot ". The hot component is an ordinary light neutrino with mass ∼ 25h 2 eV while the warm component is a sterile neutrino with mass ∼ 700h 2 eV. The two types of dark matter arise entirely within the neutrino sector and do not require separate physical origins. We calculate the linear transfer functions for a representative sample of warm-plus-hot models. The transfer functions, and results from several observational tests of structure formation, are compared with those for the cold-plus-hot models that have been studied extensively in the literature. On 1 the basis of these tests, we conclude that warm-plus-hot dark matter is essentially indistinguishable from cold-plus-hot dark matter, and therefore provides a viable scenario for large scale structure. We demonstrate that a neutrino mass matrix can be constructed which provides the requisite dark matter constituents, while remaining consistent with all cosmological bounds.