nProFit: a tool for dynamical models fitting
  The surface brightness profiles (SBPs) of star clusters hold invaluable
information on the dynamical state of clusters. The observed SBPs of star
clusters, especially that of globular clusters, are in good agreement with the
SBPs expected for isothermal spheres containing stars of reduced kinetic
energies. However, the SBPs of configurations that satisfy these theoretical
criteria cannot be uniquely expressed by analytical formulae, which had
hindered the analysis of dynamical state of observed clusters in external
galaxies. To counter this shortcoming, it has become a practice to use
empirical fitting formulae that best represent the core and halo
characteristics of theoretical models. We here present a general purpose code,
named nProFit, that allows fitting of the surface brightness profiles of
extragalactic star clusters to theoretical star clusters, defined by dynamical
models of King (1966) and Wilson (1975). In addition, we also incorporated
theoretical models that result in power-law surface brightness profiles
represented by Elson et al. 1987. The code returns the basic size parameters
such as core radius, half-light radius and tidal radius, as well as dynamically
relevant parameters, such as the volume and surface density profiles, velocity
dispersion profile, total mass and the binding energy for a user-fixed
mass-to-light ratio. The usefulness of the code in the dynamical study of
extragalactic clusters has been already illustrated in Cuevas-Otahola et al.
2020. The code, which is python-based at the user end, but makes calls to
advanced routines in Pyraf and Fortran, is now available for public use. We
provide example scripts and mock clusters in the installation package as guide
to users.
