| 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', most of which are located within r=1.1′. A V-(V-I) diagram of these objects shows a dominant vertical structure obviously consisting 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 mag and σ=1.19+/-0.09 from Gaussian fitting. From this result the distance to NGC 4472 is estimated to be d=14.7+/-1.3 Mpc, for the foreground reddening E(V-I)=0.03 and the peak luminosity for the Galactic globular clusters of MV(max)=-7.4 mag. The peak luminosity for the RGCs is similar to that for the BGCs, which indicates that the RGCs may be several gigayears younger than the BGCs. The luminosity function of the globular clusters shows little systematic variation depending on the galactocentric radius at r<4'. However, the mean luminosity of the bright BGCs decreases by 0.2 mag with increasing galactocentric radius over the range of 9', 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+/-0.01 and 1.23+/-0.01, which correspond to the metallicities of [Fe/H]=-1.41 and -0.23 dex, respectively. The mean observed color of all the globular clusters with V<23.9 mag is derived to be (V-I)=1.11+/-0.01 (m.e.), corresponding to the metallicity of [Fe/H]=-0.79+/-0.05 dex. 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. There are more RGCs than the BGCs within r~2', while there are fewer RGCs than the BGCs in the outer region of NGC 4472. Radial and azimuthal structures of the globular cluster system in NGC 4472 are also investigated. Surface number density profiles of both the BGCs and RGCs become flat in the central region, and the core radii of the globular cluster systems are measured to be rc=1.9′ for the BGCs, rc=1.2′ for the RGCs and rc=1.3′ 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. |
