Dynamical family properties and dark halo scaling relations of giant elliptical galaxies

Based on a uniform dynamical analysis of the line-profile shapes of 21 mostly luminous, slowly rotating, and nearly round elliptical galaxies, we have investigated the dynamical family relations and dark halo properties of ellipticals. Our results include : (i) The circular velocity curves (CVCs) of elliptical galaxies are flat to within similar or equal to 10% for R greater than or similar to 0.2R(e). (ii) Most ellipticals are moderately radially anisotropic; their dynamical structure is surprisingly uniform. (iii) Elliptical galaxies follow a Tully-Fisher (TF) relation with marginally shallower slope than spiral galaxies, and v(c)(max) similar or equal to 300 km s(-1) for an L-B* galaxy. At given circular velocity, they are similar to1 mag fainter in B and similar to0.6 mag in R and appear to have slightly lower baryonic mass than spirals, even for the maximum allowed by the kinematics. (iv) The luminosity dependence of M/L-B indicated by the tilt of the fundamental plane (FP) is confirmed. The tilt of the FP is not caused by dynamical or photometric nonhomology, although the latter might influence the slope of M/L versus L. It can also not be due only to an increasing dark matter fraction with L for the range of IMF currently discussed. It is, however, consistent with stellar population models based on published metallicities and ages. The main driver is therefore probably metallicity, and a secondary population effect is needed to explain the K-band tilt. (v) These results make it likely that elliptical galaxies have nearly maximal M/L-B (minimal halos). (vi) Despite the uniformly flat CVCs, there is a spread in the luminous to dark matter ratio and in cumulative M/L-B(r). Some galaxies have no indication for dark matter within 2R(e), whereas for others we obtain local M/L-B-values of 20-30 at 2R(e). (vii) In models with maximum stellar mass, the dark matter contributes similar to 10%-40% of the mass within R-e. Equal interior mass of dark and luminous matter is predicted at similar to2-4R(e). (viii) Even in these maximum stellar mass models, the halo core densities and phase-space densities are at least similar to 25 times larger and the halo core radii similar to4 times smaller than in spiral galaxies of the same circular velocity. The increase in M/L sets in at similar to 10 times larger acceleration than in spirals. This could imply that elliptical galaxy halos collapsed at high redshifts or that some of the dark matter in ellipticals might be baryonic.