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   PR # 11076
    In Einstein observatory, diffuse X-ray emission was discovered from
    most of S0 and Elliptical galaxies,and further observatories (such as
    Ginga) revealed this emission originated from hot gaseous halo. It is
    believed that mass of the hot gas is gravitationally bound by "Dark
    Matter".But is hot gas really gravitationally bound? If that is true,
    it is required to have Lx=Const.*T**3.5 relation between X-ray Lumin-
    osity (Lx) and Temperature (kT).This relation is conserved in Cluster
    of Galaxies,but uncertain in S0 and Elliptical galaxies. ASCA's spec-
    tral and imaging capabilities are necessary to determine the kT and
    Lx in wide range. Confirmation of the Lx-kT relation is the key issue
    of the origin and dynamics of the hot gas halo and binding mass,that
   is the "dark matter".
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