The Spatial Distribution of Intra-Cluster Globular Clusters in the Fornax Cluster

TL;DR

This study maps and analyzes the complex spatial distribution of intra-cluster globular clusters in the Fornax cluster, revealing over-densities, morphological features, and potential origins linked to galaxy interactions and cluster dynamics.

Contribution

It provides a detailed spatial and kinematic analysis of ICGCs in Fornax, highlighting their complex morphology and suggesting multiple formation mechanisms.

Findings

ICGCs form an elongated over-density centered on NGC 1399.

Regions with significant density enhancements deviate from simple models.

Spectroscopic velocities indicate GCs are partly stripped from host galaxies.

Abstract

We investigate the spatial distribution of the Intra-Cluster Globular Clusters (ICGCs) detected in the core of the Fornax galaxy cluster. By separately modeling different components of the observed population of Globular Clusters (GCs), we confirm the existence of an abundant ICGCs over-density with a geometrically complex, elongated morphology roughly centered on the cluster dominant galaxy NGC 1399 and stretching along the E-W direction. We identify several areas in the ICGCs distribution that deviate from a simple elliptical model and feature large density enhancements. These regions are characterized based on their statistical significance, GCs excess number, position, size and location relative to the galaxies in their surroundings. The relations between the spatial distribution and features of the ICGCs structures, mostly populated by blue GCs, and properties of the intra-cluster light and dwarf galaxies detected in the core of the Fornax cluster are described and discussed. The line-of-sight velocity distribution of spectroscopically confirmed GCs within the ICGCs structures is compatible with the systemic velocities of nearby bright galaxies in the Fornax cluster, suggesting that the ICGCs population is at least partially composed of GCs stripped from their hosts. We argue that the findings here presented suggest that, on sub-cluster scales, different mechanisms contribute to the growth of the ICGC. The western region of Fornax is likely associated with old merging events that predate the assembly of the Fornax cluster. The eastern side instead points to a mix of tidal disruption of dwarf galaxies and stripping from the GCSs of massive hosts, more typical of relaxed, high-density cluster environments.