The ACS Virgo Cluster Survey. XVII. The Spatial Alignment of Globular
  Cluster Systems With Early-Type Host Galaxies
  We study the azimuthal distribution of globular clusters (GCs) in early-type
galaxies and compare them to their host galaxies using data from the ACS Virgo
Cluster Survey. We find that in host galaxies with visible elongation (epsilon
> 0.2) and intermediate to high luminosities (M_z<-19), the GCs are
preferentially aligned along the major axis of the stellar light. The red
(metal-rich) GC subpopulations show strong alignment with the major axis of the
host galaxy, which supports the notion that these GCs are associated with
metal-rich field stars. The metal-rich GCs in lenticular galaxies show signs of
being more strongly associated with disks rather than bulges. Surprisingly, we
find that the blue (metal-poor) GCs can also show the same correlation. If the
metal-poor GCs are part of the early formation of the halo and built up through
mergers, then our results support a picture where halo formation and merging
occur anisotropically, and where the present day major axis is an indicator of
the preferred merging axis.
