The Globular Cluster Populations of Giant Galaxies: Mosaic Imaging of
  Five Moderate-Luminosity Early-Type Galaxies
  This paper presents results from wide-field imaging of the globular cluster
(GC) systems of five intermediate-luminosity (M_V ~-21 to -22) early-type
galaxies. The aim is to accurately quantify the global properties of the GC
systems by measuring them out to large radii. We obtained BVR imaging of four
lenticular galaxies (NGC 5866, NGC 4762, NGC 4754, NGC 3384) and one elliptical
galaxy (NGC 5813) using the KPNO 4m telescope and MOSAIC imager and traced the
GC population to projected galactocentric radii ranging from ~20 kpc to 120
kpc. We combine our imaging with Hubble Space Telescope data to measure the GC
surface density close to the galaxy center. We calculate the total number of
GCs (N_GC) from the integrated radial profile and find N_GC = 340 +/- 80 for
NGC 5866, N_GC = 2900 +/- 400 for NGC 5813, N_GC = 270 +/- 30 for NGC 4762,
N_GC = 115 +/- 15$ for NGC 4754, and N_GC = 120 +/- 30 for NGC 3384. The
measured GC specific frequencies are S_N between 0.6 and 3.6 and T in the range
0.9 to 4.2. These values are consistent with the mean specific frequencies for
the galaxies' morphological types found by our survey and other published data.
Three galaxies (NGC 5866, NGC 5813, NGC 4762) had sufficient numbers of GC
candidates to investigate color bimodality and color gradients in the GC
systems. NGC 5813 shows strong evidence (>3 sigma) for bimodality and a B-R
color gradient resulting from a more centrally concentrated red (metal-rich) GC
subpopulation. We find no evidence for statistically significant color
gradients in the other two galaxies.
