“…The observed flatness of the galactic rotation curved indicating the presence of dark matter halos around galaxies [108]. Summed to these evidences are the observations of the cosmic microwave background (CMB) anisotropies ( [112,57]) combined with large-scale structure and type Ia supernova luminosity data ( [100,101,102,97]) which all together constrain the cosmological parameters also finding once more that visible matter contributes only about 4% of the energy density of the Universe, gravitational lensing [99] and X-ray spectra ( [69,37,116,36,87]) in elliptical galaxies, and the high velocity dispersion and gas temperature in clusters of galaxies ( [116,74]), all of them leading to a picture in which galaxies are composed of a luminous galactic disk surrounded by a galactic halo of dark matter. Also the relative contribution of the dark matter component is usually specified in terms of the mass-to-light ratio, M/L; which reflects the total amount of mass relative to the total light within a given scale.…”