The Globular Cluster System in the Inner Region of the Giant Elliptical Galaxy NGC 4472

Abstract

We present a study of globular clusters in the inner region of the giant elliptical galaxy NGC 4472, based on the HST WFPC2 archive data. We have found about 1560 globular cluster candidates at the galactocentric radius r < 4 arcmin. V-(V-I) diagram of these objects shows a dominant vertical structure which consists obviously of two components: blue globular clusters (BGCs) and red globular clusters (RGCs). The luminosity function of the globular clusters is derived to have a peak at V(max)=23.50+/-0.16 from Gaussian fitting. The distance to NGC 4472 is estimated to be d=14.7+/-1.3 Mpc.The peak luminosity for the RGCs is similar to that for the BGCs, which indicates that the RGCs may be several Gyrs younger than the BGCs. The mean luminosity of the bright BGCs decreases by 0.2 mag with increasing galactocentric radius over the range of 9 arcmin, while that of the RGCs does not. The observed color distribution of these globular clusters is distinctively bimodal with peaks at (V-I) = 0.98 and 1.23. The mean observed color of all the globular clusters with V < 23.9 mag is derived to be (V-I)=1.11. These colors are exactly the same as those for the globular clusters in M87. It is found that the relative number of the BGCs to the RGCs is increasing with the increasing galactocentric radius. Surface number density profiles of both the BGCs and RGCs get flat in the central region, and the core radii of the globular cluster systems are measured to be r_c = 1.9 arcmin for the BGCs, r_c = 1.2 arcmin for the RGCs, and r_c = 1.3 arcmin for the total sample, which are much larger than the stellar core of the galaxy. In general the properties of the globular clusters in the inner region of NGC 4472 are consistent with those of the globular clusters in the outer region of NGC 4472.Comment: 27 pages (AASLaTex), 22 Postscript Figures, Accepted for Publication in the Astronomical Journal, Jul. 31st, 200