The Globular Cluster System in the Outer Regions of NGC 4472

We have undertaken a study of the globular cluster (GC) systems of a largesample of elliptical and spiral galaxies in order to test predictions of galaxyformation models. Here we present results for the giant Virgo elliptical NGC4472 (M49). The galaxy was observed in 3 filters (BVR) using the Mosaic Imageron the Kitt Peak 4-m telescope. Our images roughly double the radial coverageof previous CCD observations of NGC 4472. We have combined the Mosaic data withspectroscopic data and HST data in order to fully characterize the level ofcontamination in our GC sample. The radial profile of the GC system is fitfairly well by a de Vaucouleurs law out to 17 arc minutes (~80 kpc), but theprofile falls slightly below the de Vaucouleurs law between 17 and 23 arcminutes. The bimodal color distribution observed in past studies appears in ourdata. We find a small metallicity gradient in the inner 8 arc minutes of the GCsystem due to the increasing ratio of blue to red clusters. The gradientvanishes, however, when the entire radial extent of the data is taken intoaccount. 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 issmaller than that found by previous studies of NGC 4472. We examine theimplications of these results with regard to predictions made by four galaxyformation models, and find that all four models have at least one inconsistencywith the data. [abridged]Comment: 38 pages, incl. 10 figures and 3 tables; accepted for publication in The Astronomical Journal, January 2001 issu