THE SLOAN LENS ACS SURVEY. X. STELLAR, DYNAMICAL, AND TOTAL MASS CORRELATIONS OF MASSIVE EARLY-TYPE GALAXIES

Abstract

We use stellar masses, photometry, lensing, and velocity dispersions to\ninvestigate empirical correlations for the final sample of 73 early-type lens\ngalaxies (ETGs) from the SLACS survey. The traditional correlations\n(Fundamental Plane [FP] and its projections) are consistent with those found\nfor non-lens galaxies, supporting the thesis that SLACS lens galaxies are\nrepresentative of massive ETGs. The addition of strong lensing estimates of the\ntotal mass allows us to gain further insights into their internal structure: i)\nthe mean slope of the total mass density profile is <gamma'> = 2.078+/-0.027\nwith an intrinsic scatter of 0.16+/-0.02; ii) gamma' correlates with effective\nradius and central mass density, in the sense that denser galaxies have steeper\nprofiles; iii) the dark matter fraction within reff/2 is a monotonically\nincreasing function of galaxy mass and size; iv) the dimensional mass M_dim is\nproportional to the total mass, and both increase more rapidly than stellar\nmass M*; v) the Mass Plane (MP), obtained by replacing surface brightness with\nsurface mass density in the FP, is found to be tighter and closer to the virial\nrelation than the FP and the M*P, indicating that the scatter of those\nrelations is dominated by stellar population effects; vi) we construct the\nFundamental Hyper-Plane by adding stellar masses to the MP and find the M*\ncoefficient to be consistent with zero and no residual intrinsic scatter. Our\nresults demonstrate that the dynamical structure of ETGs is not scale invariant\nand that it is fully specified by the total mass, r_eff, and sigma. Although\nthe basic trends can be explained qualitatively in terms of varying star\nformation efficiency as a function of halo mass and as the result of dry and\nwet mergers, reproducing quantitatively the observed correlations and their\ntightness may be a significant challenge for galaxy formation models.\n