VEGAS-SSS. A VST survey of elliptical galaxies in the southern
  hemisphere: analysis of small stellar systems. Testing the methodology on the
  globular cluster system in NGC3115
  We present a study of globular clusters (GCs) and other small stellar systems
(SSSs) in the field of NGC3115, observed as part of the VEGAS imaging survey,
carried out with the VST telescope. We use deep g and i data of NGC3115, a
well-studied lenticular galaxy with excellent scientific literature. This is
fundamental to test the methodologies, verify the results, and probe the
capabilities of the VEGAS-SSS. Leveraging the large field of view of the VST
allow us to accurately study of the distribution and properties of SSSs as a
function of galactocentric distance Rgc, well beyond ~20 galaxy effective
radii, in a way not often possible. Our analysis of colors, magnitudes and
sizes of SSS candidates confirms the results from existing studies, some of
which carried out with 8-10m class telescopes, and further extends them to
unreached Rgc distances, with similar accuracy. We find a color bimodality for
the GC population and a r1/4 profile for the surface density of GCs as for the
galaxy light profile. The radial color gradient of blue and red GCs previously
found, for instance by the SLUGGS survey, is further extended out to the
largest Rgc inspected, ~65 kpc. The surface density profiles of blue and red
GCs taken separately are well approximated by a r1/4 density profile, with the
fraction of blue GCs being slightly larger at larger Rgc. We do not find hints
of a trend for the red GC and for the GC turnover magnitude to vary with
radius, but we observe a ~0.2 mag difference in the turnover magnitude of the
blue and red GCs subpopulations. Inspecting SSS sizes and colors we obtained a
list of UCDs and GC candidates suitable for future spectroscopic follow-up. In
conclusion, our study shows the reliability of the methodologies developed to
study SSSs in the field of bright early-type galaxies, and the great potential
of the VEGAS survey to produce original results on SSSs science.
