1208.3522 (Michele Cappellari et al.)

The Atlas3D project - XIX. Benchmark for early-type galaxies scaling relations from 260 dynamical models: mass-to-light ratio, dark matter, Fundamental Plane and Virial Plane    [PDF]

Michele Cappellari, Nicholas Scott, Katherine Alatalo, Leo Blitz, Maxime Bois, Frederic Bournaud, M. Bureau, Alison F. Crocker, Roger L. Davies, Timothy A. Davis, P. T. de Zeeuw, Pierre-Alain Duc, Sadegh Khochfar, Davor Krajnovic, Harald Kuntschner, Richard M. McDermid, Raffaella Morganti, Thorsten Naab, Tom Oosterloo, Marc Sarzi, Paolo Serra, Anne-Marie Weijmans, Lisa M. Young

We study the volume-limited Atlas3D sample of 260 early-type galaxies. We construct detailed axisymmetric dynamical models, which allow for orbital anisotropy, include a dark matter halo, and reproduce in detail both the galaxy images and the high-quality integral-field stellar kinematics out to about 1Re, the projected half-light radius. We derive accurate total (M/L)_e and dark matter fractions f_DM, within a sphere of radius r=Re. We infer masses M_JAM and stellar (M/L)_stars. We find that the thin two-dimensional subset spanned by galaxies in the (M_JAM,sigma_e,R_e^max) coordinates system, which we call the Virial Plane (VP) has an observed rms scatter of 17%, which would imply an intrinsic one of just 4%. The VP satisfies the scalar virial relation M_JAM=5.0*sigma_e^2 R_e^max/G within our tight errors. However, the details of how both Re and sigma_e are determined are critical in defining the precise deviation from this simple virial form. We measure a median dark matter fractions of f_DM=16% in our sample, which implies the total density profile within 1Re is dominated by the stellar density. When approximated by a power-law the latter has the `isotermal' form rho_stars ~ r^-2.0 with an intrinsic rms scatter of 0.2. The (M/L)_e-sigma_e relation, which describes most of the deviations between the VP and the FP is (M/L)_e ~ sigma_e^0.69. This relation provides an upper limit to any increase of the IMF mass normalization with sigma_e. We study the relations between sigma_e and the galaxies circular velocity within 1Re and find the two empirical relations V_c(R_e^max) ~ 1.51*sigma_e and max(V_circ) ~ 1.76*sigma_e. [Abridged]

View original: http://arxiv.org/abs/1208.3522