The Globular Cluster System of the Spiral Galaxy NGC 7814

We present the results of a wide-field photometric study of the globularcluster (GC) system of the edge-on Sab spiral NGC7814. This is the first spiralto be fully analyzed from our survey of the GC systems of a large sample ofgalaxies beyond the Local Group. NGC7814 is of particular interest because aprevious study estimated that it has 500-1000 GCs, giving it the largestspecific frequency (S_N) known for a spiral. Understanding this galaxy's GCsystem is important in terms of our understanding of the GC populations ofspirals in general and has implications for the formation of massive galaxies.We observed the galaxy in BVR filters with the WIYN 3.5-m telescope, and usedimage classification and three-color photometry to select GC candidates. Wealso analyzed archival HST WFPC2 images of NGC7814, both to help quantify thecontamination level of the WIYN GC candidate list and to detect GCs in theinner part of the galaxy halo. Combining HST data with high-qualityground-based images allows us to trace the entire radial extent of thisgalaxy's GC system and determine the total number of GCs directly throughobservation. We find that rather than being an especially high-S_N spiral,NGC7814 has <200 GCs and S_N ~ 1, making it comparable to the two mostwell-studied spirals, the Milky Way and M31. We explore the implications ofthese results for models of the formation of galaxies and their GC systems. Theinitial results from our survey suggest that the GC systems of typicalellipticals can be accounted for by the merger of two or more spirals, but thatfor highly-luminous ellipticals, additional physical processes may be needed.Comment: 28 pages, incl. 4 figures; accepted for publication in The Astronomical Journal, November 2003 issu