Let G be a real linear reductive group and let H be a unimodular, locally algebraic subgroup. Let supp L 2 (G/H) be the set of irreducible unitary representations of G contributing to the decomposition of L 2 (G/H), namely the support of the Plancherel measure. In this paper, we will relate supp L 2 (G/H) with the image of moment map from the cotangent bundleFor the homogeneous space X = G/H, we attach a complex Levi subgroup L X of the complexification of G and we show that in some sense "most" of representations in supp L 2 (G/H) are obtained as quantizations of coadjoint orbits O such that O ≃ G/L and that the complexification of L is conjugate to L X . Moreover, the union of such coadjoint orbits O coincides asymptotically with the moment map image. As a corollary, we show that L 2 (G/H) has a discrete series if the moment map image contains a nonempty subset of elliptic elements.2010 Mathematics Subject Classification. 22E46.