Globular Cluster Systems of Spiral and S0 Galaxies: Results from WIYN Imaging of NGC1023, NGC1055, NGC7332 and NGC7339

TL;DR

This study analyzes the globular cluster systems of four spiral and S0 galaxies using WIYN imaging, determining their distributions, total numbers, and evidence for multiple populations, contributing new data on GC systems in these galaxy types.

Contribution

It provides new measurements of GC populations, distributions, and bimodality evidence in spiral and S0 galaxies, combining WIYN data with HST and Keck observations.

Findings

Total GC counts range from 75 to 490 across the galaxies.

Evidence for bimodal color distributions in NGC1023 and NGC7332.

Identification of GC candidates associated with a satellite galaxy.

Abstract

We present results from a study of the globular cluster (GC) systems of four spiral and S0 galaxies imaged as part of an ongoing wide-field survey of the GC systems of giant galaxies. The target galaxies -- the SB0 galaxy NGC1023, the SBb galaxy NGC1055, and an isolated pair comprised of the Sbc galaxy NGC7339 and the S0 galaxy NGC7332 -- were observed in BVR filters with the WIYN 3.5-m telescope and Minimosaic camera. For two of the galaxies, we combined the WIYN imaging with previously-published data from the Hubble Space Telescope and the Keck Observatory to help characterize the GC distribution in the central few kiloparsecs. We determine the radial distribution (surface density of GCs versus projected radius) of each galaxy's GC system and use it to calculate the total number of GCs (N_GC). We find N_GC = 490+/-30, 210+/-40, 175+/-15, and 75+/-10 for NGC1023, NGC1055, NGC7332, and NGC7339, respectively. We also calculate the GC specific frequency (N_GC normalized by host galaxy luminosity or mass) and find values typical of those of the other spiral and E/S0 galaxies in the survey. The two lenticular galaxies have sufficient numbers of GC candidates for us to perform statistical tests for bimodality in the GC color distributions. We find evidence at a high confidence level (>95%) for two populations in the B-R distribution of the GC system of NGC1023. We find weaker evidence for bimodality (>81% confidence) in the GC color distribution of NGC7332. Finally, we identify eight GC candidates that may be associated with the Magellanic dwarf galaxy NGC1023A, a satellite of NGC1023.