Isolated elliptical galaxies and their globular cluster systems. II. NGC
  7796 - globular clusters, dynamics, companion
  We investigate the globular cluster system of the isolated elliptical NGC
7796, present new photometry of the galaxy, and use published kinematical data
to constrain the dark matter content. Deep images in B and R, obtained with the
VIsible MultiObject Spectrograph (VIMOS) at the VLT, form the data base. We
present isotropic and anisotropic Jeans-models and give a morphological
description of the companion dwarf galaxy. The globular cluster system has
about 2000 members, so it is not as rich as those of giant ellipticals in
galaxy clusters with a comparable stellar mass, but richer than many cluster
systems of other isolated ellipticals. The colour distribution of GCs is
bimodal, which does not necessarily mean a metallicity bimodality. The
kinematic literature data are somewhat inconclusive. The velocity dispersion in
the inner parts can be reproduced without dark matter under isotropy. Radially
anisotropic models need a low stellar mass-to-light ratio, which would contrast
with the old age of the galaxy. A MONDian model is supported by X-ray analysis
and previous dynamical modelling, but better data are necessary for a
confirmation. The dwarf companion galaxy NGC 7796-1 exhibits tidal tails,
multiple nuclei, and very boxy isophotes. NGC 7796 is an old, massive isolated
elliptical galaxy with no indications of later major star formation events as
seen frequently in other isolated ellipticals. Its relatively rich globular
cluster system shows that isolation does not always mean a poor cluster system.
The properties of the dwarf companion might indicate a dwarf-dwarf merger.
(abridged)
