paper

Washington Photometry of the Globular Cluster System of NGC 4472. II. The Luminosity Function and Spatial Structure

arXiv:astro-ph/9711194 · doi:10.1086/300249

Abstract

We present a comprehensive study of the luminosity function and spatial structure of the globular cluster system of NGC 4472, based on deep wide field Washington CT1 CCD images. The globular cluster luminosity function shows a peak at T1=23.3 +/- 0.1 mag, about 1.5 mags brighter than our 50% completeness limit. We estimate the true distance modulus to NGC 4472 to be (m-M)o = 31.2 +/- 0.2. With our large sample (~ 2000) of bright globular clusters over a wide field, we make a definitive investigation of the spatial structures of the metal-poor and metal-rich cluster populations and find that they are systematically different: (1) The metal-rich clusters are more centrally concentrated than the metal-poor clusters; and (2) The metal-rich clusters are elongated roughly along the major axis of the parent galaxy, while the metal-poor clusters are essentially spherically distributed. In general, the metal-rich clusters closely follow the underlying halo starlight of NGC 4472 in terms of spatial structure and metallicity, while the metal-poor clusters do not. The global value of the specific frequency of the globular clusters in NGC 4472 is estimated to be S_N = 4.7 +/- 0.6. The local specific frequency increases linearly outward from the center of NGC 4472 until ~ 5'.5, beyond which it levels off at S_N ~ 8.5 until the limit of our data at 7'. The specific frequency of both the metal-rich and metal-poor populations shows similar behavior. However, S_N of the metal-poor clusters is about a factor 2 larger than that of the metal-rich clusters in the outer regions. Implications of these results for the origin of the globular clusters in NGC 4472 are discussed.

28 Pages (AASLaTeX), 9 Postscript figures, Accepted for publicaion in the Astronomical Journal, Mar. 31st, 1998

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