2007ApJ...668..209C

We perform a detailed study of the globular cluster (GC) system in the galaxy NGC 5866 based on F435W, F555W, and F625W (~B, V, and R) Hubble Space Telescope Advanced Camera for Surveys images. Adopting color, size, and shape selection criteria, the final list of GC candidates comprises 109 objects, with small estimated contamination from background galaxies, and foreground stars. The color distribution of the final GC sample has a bimodal form. Adopting color to metallicity transformations derived from the Teramo-SPoT simple stellar population model, we estimate a metallicity [Fe/H]~-1.5 and -0.6 dex for the blue and red peaks, respectively. A similar result is found if the empirical color-metallicity relations derived from Galactic GC data are used. The two subpopulations show some of the features commonly observed in the GC system of other galaxies, like a ``blue tilt'', higher central concentrations of the red subsystem, and larger half-light radii at larger galactocentric distances. However, we do not find evidence of a substantial difference between the average sizes of red and blue clusters. Our analysis of the GC luminosity function indicates a V-band turnover magnitude V^TOM₀=23.46±0.06, or M^TOM_V,0~-7.29±0.10 mag, using the distance modulus derived from the average of surface brightness fluctuation (SBF) and the planetary nebula luminosity function (PNLF) distances. The absolute turnover magnitude obtained agrees well with calibrations from literature. The specific frequency is measured to be S_N=1.4±0.3, typical for galaxies of this type.