The extremely populated globular cluster system of the lenticular galaxy
  NGC 6861
  We present a photometric study of the globular cluster (GC) system associated
to the lenticular galaxy (S0) NGC 6861, which is located in a relatively low
density environment. It is based on GEMINI/GMOS images in the filters g', r',
i' of three fields, obtained under good seeing conditions. Analyzing the
colour-magnitude and colour-colour diagrams, we find a large number of GC
candidates, which extends out to 100 kpc, and we estimate a total population of
3000+/-300 GCs. Besides the well known blue and red subpopulations, the colour
distribution shows signs of the possible existence of a third subpopulation
with intermediate colours. This could be interpreted as evidence of a past
interaction or fusion event. Other signs of interactions presented by the
galaxy, are the non-concentric isophotes and the asymmetric spatial
distribution of GC candidates with colours (g'-i')_0>1.16. As observed in other
galaxies, the red GCs show a steeper radial distribution than the blue GCs. In
addition, the spatial distribution of these candidates exhibit strong signs of
elongation. This feature is also detected in the intermediate subpopulation. On
the other hand, the blue candidates show an excellent agreement with the X-ray
surface brightness profile, outside 10 kpc. They also show a colour-luminosity
relation (blue-tilt), similar to that observed in other galaxies. A new
distance modulus has been estimated through the blue subpopulation, which is in
good agreement with the previous value obtained through the surface brightness
fluctuations method. The specific frequency of NGC 6861 (Sn=10.6+/-2.1) is
probably one of the highest values obtained for an S0 galaxy so far.
