The Globular Cluster System in the Outer Regions of NGC 4472

Abstract

We have undertaken a study of the globular cluster (GC) systems of a large sample of elliptical and spiral galaxies in order to test predictions of galaxy formation models. Here we present results for the giant Virgo elliptical NGC 4472 (M49). The galaxy was observed in 3 filters (BVR) using the Mosaic Imager on the Kitt Peak 4-m telescope. Our images roughly double the radial coverage of previous CCD observations of NGC 4472. We have combined the Mosaic data with spectroscopic data and HST data in order to fully characterize the level of contamination in our GC sample. The radial profile of the GC system is fit fairly well by a de Vaucouleurs law out to 17 arc minutes (~80 kpc), but the profile falls slightly below the de Vaucouleurs law between 17 and 23 arc minutes. The bimodal color distribution observed in past studies appears in our data. We find a small metallicity gradient in the inner 8 arc minutes of the GC system due to the increasing ratio of blue to red clusters. The gradient vanishes, however, when the entire radial extent of the data is taken into account. We estimate a total of 5,900 GCs in NGC 4472 out to 23 arc minutes, yielding a specific frequency of 3.6+/-0.6 within this radius. This value is smaller than that found by previous studies of NGC 4472. We examine the implications of these results with regard to predictions made by four galaxy formation models, and find that all four models have at least one inconsistency with the data. [abridged]