SPATIAL STRUCTURES IN THE GLOBULAR CLUSTER DISTRIBUTION OF THE 10 BRIGHTEST VIRGO GALAXIES

Abstract

We report the discovery of significant localized structures in the projected two-dimensional (2D) spatial distributions of the Globular Cluster (GC) systems of the ten brightest galaxies in the Virgo Cluster. We use catalogs of GCs extracted from the HST ACS Virgo Cluster Survey (ACSVCS) imaging data, complemented, when available, by additional archival ACS data. These structures have projected sizes ranging from $\sim\!5$ arcsec to few arc-minutes ($\sim\!1$ to $\sim\!25$ kpc). Their morphologies range from localized, circular, to coherent, complex shapes resembling arcs and streams. The largest structures are preferentially aligned with the major axis of the host galaxy. A few relatively smaller structures follow the minor axis. Differences in the shape and significance of the GC structures can be noticed by investigating the spatial distribution of GCs grouped by color and luminosity. The largest coherent GC structures are located in low-density regions within the Virgo cluster. This trend is more evident in the red GC population, believed to form in mergers involving late-type galaxies. We suggest that GC over-densities may be driven by either accretion of satellite galaxies, major dissipationless mergers or wet dissipation mergers. We discuss caveats to these scenarios, and estimate the masses of the potential progenitors galaxies. These masses range in the interval $10^{8.5}\!-\!10^{9.5}$ solar masses, larger than those of the Local Group dwarf galaxies.