Testing lowered isothermal models with direct N-body simulations of
  globular clusters
  Several self-consistent models have been proposed, aiming at describing the
phase space distribution of stars in globular clusters. This study explores the
ability of the recently proposed LIMEPY models (Gieles & Zocchi) to reproduce
the dynamical properties of direct N-body models of a cluster in a tidal field,
during its entire evolution. These dynamical models include prescriptions for
the truncation and the degree of radially-biased anisotropy contained in the
system, allowing us to explore the interplay between the role of anisotropy and
tides in various stages of the life of star clusters. We show that the amount
of anisotropy in an initially tidally underfilling cluster increases in the
pre-collapse phase, and then decreases with time, due to the effect of the
external tidal field on its spatial truncation. This is reflected in the
correspondent model parameters, and the best-fit models reproduce the main
properties of the cluster at all stages of its evolution, except for the phases
immediately preceding and following core collapse. We also notice that the
best-fit LIMEPY models are significantly different from isotropic King models,
especially in the first part of the evolution of the cluster. Our results put
limits on the amount of radial anisotropy that can be expected for clusters
evolving in a tidal field, which is important to understand other factors that
could give rise to similar observational signatures, such as the presence of an
intermediate-mass black hole.
