Dark matter halos in elliptical galaxies

Values of the M/L(B) ratio in the inner regions of elliptical (E) galaxies are determined using ionized gas disks as tracers of the triaxial potential. These data, when combined with those provided by the H I disks extending to the outer regions, show that the variation of M/L(B) with galactocentric radius in Es is similar to that of spirals. In particular, it is found that in spirals and Es of the same visible mass the radius where the density of the dark matter equals that of the visible matter occurs at the same distance in units of r(e), namely at 1.2r(e). This suggests a similar picture of baryonic collapse into a preexisting DM halo for both Es and spirals.