The ACS Fornax Cluster Survey. XII. Diffuse Star Clusters in Early-type Galaxies

Abstract

Diffuse star clusters (DSCs) are old and dynamically hot stellar systems that have lower surface brightness and more extended morphology than globular clusters (GCs). Using the images from HST/ACS Fornax Cluster Survey, we find that 12 out of 43 early-type galaxies (ETGs) in the Fornax cluster host significant numbers of DSCs. Together with literature data from the HST/ACS Virgo Cluster Survey, where 18 out of 100 ETGs were found to host DSCs, we systematically study the relationship of DSCs with GCs, and their host galaxy environment. Two DSC hosts are post-merger galaxies, with most of the other hosts either having low mass or showing clear disk components. We find that while the number ratio of DSCs to GCs is nearly constant in massive galaxies, the DSC-to-GC ratio becomes systematically higher in lower mass hosts. This suggests that DSCs may be more efficient at forming (or surviving) in low density environments. DSC hosts are not special either in their position in the cluster, or in the galactic color-magnitude diagram. Why some disk and low-mass galaxies host DSCs while others do not is still a puzzle, however. The mean ages of DSC hosts and non-hosts are similar at similar masses, implying that formation efficiency, rather than survival, is the reason behind different DSC number fractions in early-type galaxies.

13 pages, 12 figures; accepted by ApJ

References in corpus (8)

• The Atlas3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies
• The ACS Virgo Cluster Survey XV. The Formation Efficiencies of Globular Clusters in Early-Type Galaxies: The Effects of Mass and Environment
• The ACS Fornax Cluster Survey. I. Introduction to the Survey and Data Reduction Procedures
• Variations in Stellar Clustering with Environment: Dispersed Star Formation and the Origin of Faint Fuzzies
• The Next Generation Virgo Cluster Survey. VI. The Kinematics of Ultra-compact Dwarfs and Globular Clusters in M87
• The Next Generation Virgo Cluster Survey. XII. Stellar Populations and Kinematics of Compact, Low-Mass Early-Type Galaxies from Gemini GMOS-IFU Spectroscopy
• Scl-dE1 GC1: An Extended Globular Cluster in a Low-Luminosity Dwarf Elliptical Galaxy
• A Catalog of Bright Star Clusters in the Interacting Galaxy M51

Cited by in corpus (8)

• Ultra-Diffuse Galaxies in the Perseus Cluster: Comparing Galaxy Properties with Globular Cluster System Richness
• The ACS Fornax Cluster Survey. III. Globular Cluster Specific Frequencies of Early-Type Galaxies
• The Next Generation Virgo Cluster Survey. XXXIV. Ultra-Compact Dwarf (UCD) Galaxies in the Virgo Cluster
• Luminosity functions of globular clusters in five nearby spiral galaxies using HST/ACS images
• A metal-poor ultra compact dwarf galaxy at a kiloparsec distance from the low-mass elliptical galaxy FCC47
• The complex globular cluster system of the S0 galaxy NGC 4382 in the outskirts of the Virgo Cluster
• Field/Isolated lenticular galaxies with high $S_N$ values: the case of NGC 4546 and its globular cluster system
• Low-density star cluster formation: discovery of a young faint fuzzy on the outskirts of the low-mass spiral galaxy NGC 247