The SLUGGS Survey: The Inner Dark Matter Density Slope of the Massive
  Elliptical Galaxy NGC 1407
  We investigate the dark matter density profile of the massive elliptical
galaxy, NGC 1407, by constructing spherically symmetric Jeans models of its
field star and globular cluster systems. Two major challenges in such models
are the degeneracy between the stellar mass and the dark matter halo profiles,
and the degeneracy between the orbital anisotropy of the tracer population and
the total mass causing the observed motions. We address the first issue by
using new measurements of the mass-to-light ratio profile from stellar
population constraints that include a radially varying initial mass function.
To deal with the mass--anisotropy degeneracy, we make use of multiple kinematic
tracers, including two subpopulations of globular clusters in addition to the
galaxy's field stars. We create a hierarchical Bayesian model that addresses
several often neglected systematic uncertainties, such as the statistical
weight given to various datasets and the adopted distance. After sampling the
posterior probability distribution with a Markov Chain Monte Carlo method, we
find evidence for a central cusp with a log-slope of $\gamma =
1.0^{+0.3}_{-0.4}$. This is lower than expected for dark matter halos that have
undergone adiabatic contraction, supporting inferences from gravitational
lensing that some process has suppressed the steepening of halos in massive
galaxies. We also confirm radially-biased orbits for the metal-rich globular
clusters and tangentially-biased orbits for the metal-poor globular clusters,
which remains a puzzling finding for an accretion-dominated halo.
