This paper presents results from wide-field imaging of the globular cluster (GC) systems of five intermediate-luminosity (MV ~ –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 4?m 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 SN between 0.6 and 3.6 and T in the range 0.9-4.2. 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, and NGC?4762) had sufficient numbers of GC candidates to investigate color bimodality and color gradients in the GC?systems. NGC?5813 shows strong evidence (3σ) 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.
展开▼
