Global properties of the globular cluster systems of four spiral galaxies

We present results from a wide- field imaging study of the globular cluster ( GC) systems of a sample of edge- on, Sb-Sc spiral galaxies similar to 7 - 20 Mpc away. This study is part of a larger survey of the ensemble properties of the GC populations of giant galaxies. We imaged the galaxies in BVR filters with large- format CCD detectors on the WIYN 3.5 m telescope to projected radii of similar to 20 - 40 kpc. For four galaxies ( NGC 2683, NGC 3556, NGC 4157, and NGC 7331), we quantify the radial distributions of the GC systems and estimate the total number, luminosity- and mass- normalized specific frequencies (S-N and T), and blue ( metal-poor) fraction of GCs. A fifth galaxy ( NGC 3044) was apparently too distant for us to have detected its GC system. Our S-N for NGC 2683 is 2.5 times smaller than the previously published value, likely due in part to reduced contamination from non-GCs. For the spiral galaxies analyzed for the survey to date, the average number of GCs is 170 +/- 40, and the weighted mean values of S-N and T are 0.8 +/- 0.2 and 1.4 +/- 0.3, respectively. We use the survey data to derive a relationship between the radial extent of the GC system and host galaxy mass over a factor of 20 in mass. Finally, we confirm the trend, identified in previous survey papers, of increasing specific frequency of metal- poor GCs with increasing galaxy mass. We compare the data with predictions from a simple model and show that carefully quantifying the numbers of metal- poor GCs in galaxies can constrain the formation redshifts of the GCs and their host galaxies.