Global Properties of the Globular Cluster Systems of Four Spiral Galaxies

Abstract

We present results from a wide-field imaging study of the globular cluster (GC) systems of a sample of edge-on, SbSc spiral galaxies $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 $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 AE 40, and the weighted mean values of S N and T are 0:8 AE 0:2 and 1:4 AE 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.

Are Globular Clusters the Remnant Nuclei of Progenitor Disk Galaxies?

“…Because any intermediate merger products are created from identical building blocks as described in assumption 1, the number of GCs simply scales linearly with assembled galaxy mass, regardless of the details of the merger tree. This offers a natural explanation for the empirical result that all but the latest type spirals (see § 5) show a constant specific frequency of GCs: the observed Tvalue (Zepf & Ashman 1993) is ∼2 GCs per 10 9 M , (Goudfrooij et al 2003;Rhode et al 2007). This value is likely a lower limit because (i) not all GCs will survive and (ii) the faintest GCs might be missed in surveys.…”

How large are the globular cluster systems of early-type galaxies and do they scale with galaxy halo properties?

“…This constant density background is assumed to be due to contaminants in the photometric object list. This approach has been taken by Rhode et al (2007Rhode et al ( , 2010 and Kartha et al (2016).…”

The Formation of Spheroids in Early-Type Spirals: Clues From Their Globular Clusters

“…THP acknowledges support in form of the Plaskett Research Fellowship at the Herzberg Institute of Astrophysics of the National Research Council of Canada Chandar et al (2004). The dotted lines show the range of values seen for the total S N in late-type spirals (Goudfrooij et al 2003) while the dashed line depicts a least-square fit to the S N of blue clusters (Rhode et al 2007). Right: The number of red clusters as a function of the bulge V luminosity.…”

“…For our sample galaxies, values for both the total S N and the blue S N are shown. Total S N values for early-type and late-type spirals from Goudfrooij et al (2003), Rhode et al (2007), and Chandar et al (2004) are also shown. We see that our blue S N values (0.34 -0.84) mostly lie within the typical S N values for late-type spirals (0.55±0.25) found by these authors.…”