The Atlas3D project - XV. Benchmark for early-type galaxies scaling
  relations from 260 dynamical models: mass-to-light ratio, dark matter,
  Fundamental Plane and Mass Plane
  We study the volume-limited and nearly mass selected (stellar mass M>6*10^9
Msun) Atlas3D sample of 260 early-type galaxies. We construct detailed
axisymmetric dynamical models (JAM), 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. We derive accurate total
M/L and dark matter fractions f_DM, within a sphere of radius r=Re. We also
measure the stellar M/L and derive a median dark matter fraction f_DM=13%. We
find that the thin two-dimensional subset spanned by galaxies in the
(M_JAM,sigma_e,R_e) coordinates system, which we call the Mass Plane (MP) has
an observed rms scatter of 19% and an intrinsic one of 11%. The MP satisfies
the scalar virial relation M_JAM sigma_e^2 R_e within our tight errors.
However, the details of how both Re and sigma_e are determined are critical in
defining the precise deviation from the virial exponents. We revisit the
(M/L)-sigma_e relation, which describes most of the deviations between the MP
and the FP. The best-fitting relation is (M/L) sigma_e^0.72 (r-band). It
provides an upper limit to any systematic increase of the IMF mass
normalization with sigma_e. We study of the link between sigma_e and the
galaxies circular velocity V_circ within 1Re (where stars dominate) and find
the relation max(V_circ)~1.76*sigma_e, which has an observed scatter of 7%. The
accurate parameters described in this paper are used in the companion Paper XX
of this series to explore the variation of global galaxy properties, including
the IMF, on the projections of the MP. [Abridged]
