A VST and VISTA study of globular clusters in NGC253
  Aims. We analyze the properties of the sources in the NGC253 to define an up
to date catalog of GC candidates in the galaxy. Methods. Our analysis is based
on the science verification data of two ESO survey telescopes, VST and VISTA.
Using ugri photometry from VST and JKs from VISTA, GC candidates were selected
using the morpho-photometric and color properties of spectroscopically
confirmed GCs available in the literature. The strength of the results was
verified against available archival HST/ACS data from the GHOSTS survey.
Results. The adopted GC selection leads to the definition of a sample of ~350
GC candidates. At visual inspection, we find that 82 objects match all the
requirements for selecting GC candidates and 155 are flagged as uncertain GC
candidate; 110 are unlikely GCs, most likely background galaxies. Furthermore,
our analysis shows that four of the previously spectroscopically confirmed GCs,
i.e., ~20% of the total spectroscopic sample, are more likely either background
galaxies or high-velocity Milky Way stars. The radial density profile of the
selected best candidates shows the typically observed r1/4-law radial profile.
The analysis of the color distributions reveals only marginal evidence of the
presence of color bimodality, which is normally observed in galaxies of similar
luminosity. The GC luminosity function does not show the typical symmetry,
mainly because of the lack of bright GCs. Part of the bright GCs missing might
be at very large galactocentric distances or along the line of sight of the
galaxy dusty disk. Conclusions. Using ugriJKs photometry we purged the list of
GCs with spectroscopic membership and photometric GC candidates in NGC 253. Our
results show that the use of either spectroscopic or photometric data only does
not generally ensure a contaminant-free sample and a combination of both
spectroscopy and photometry is preferred.
