Connection Between Dwarf Galaxies and Globular Clusters: Insights from the Perseus Cluster Using Subaru Imaging and Keck Spectroscopy

We present a systematic study of 189 dwarf galaxies and their globular cluster (GC) systems in the Perseus cluster, based on deep Subaru Hyper Suprime-Cam imaging and Keck spectroscopy, supplemented by literature data. This constitutes the largest sample of dwarfs in a single galaxy cluster to date with simultaneous deep imaging, spectroscopic coverage, and GC measurements, while uniquely spanning a broad and continuous range of galaxy properties. We find an anti-correlation between GC specific mass and galaxy stellar mass for dwarfs in Perseus similar to observations in other clusters. At fixed stellar mass, dwarfs with lower surface brightness or larger effective radius tend to be more GC-rich – suggesting either high GC formation efficiency in an earlier compact-galaxy phase, or less efficient GC disruption. The correlation between GC richness and axis ratio in Perseus is weaker than in other environments. We find some connection between GC richness and infall time, but not with the clear correlations found in Virgo, Coma, and cosmological simulations. More complete observations are needed to test for cluster-to-cluster variations in galaxy and GC evolutionary histories. This work demonstrates the potential of new wide-field imaging and spectroscopy surveys for understanding GCs and dwarf galaxies, and highlights the need for further work in theoretical modeling.

💡 Research Summary

This paper presents a comprehensive study of the connection between dwarf galaxies and their globular cluster (GC) systems within the Perseus galaxy cluster, one of the most massive clusters in the nearby universe. The analysis is based on a sample of 189 dwarf galaxies, the largest such sample in a single cluster with simultaneous deep imaging, spectroscopic coverage, and GC measurements. Primary data comes from deep Subaru Hyper Suprime-Cam (HSC) imaging in g, r, and i bands and Keck spectroscopy (DEIMOS and KCWI), supplemented by archival Hubble Space Telescope (HST) data, literature spectroscopy for membership confirmation, and recent GC catalogs from Euclid observations.

The study confirms the known anti-correlation between GC specific frequency (or mass) and host galaxy stellar mass for dwarf galaxies, meaning lower-mass dwarfs tend to have a higher fraction of their mass in GCs on average. The key new insight comes from examining trends at fixed stellar mass. The authors find that, among dwarfs of similar mass, those with lower central surface brightness or larger effective radii tend to be richer in GCs. This correlation suggests that either GC formation was more efficient during an earlier, more compact phase of these galaxies, or that the more diffuse structure of these galaxies leads to less efficient GC disruption (e.g., by tidal shocks) in the cluster environment.

A significant focus is placed on ultra-diffuse galaxies (UDGs), which often lie at the extreme end of this trend, possessing surprisingly rich GC systems for their low stellar mass and large size. This finding adds weight to scenarios where such UDGs are “failed galaxies” that experienced intense early star formation (producing many GCs) followed by rapid quenching, rather than simply being puffed-up versions of normal dwarfs.

Interestingly, the study finds that the correlation between GC richness and galaxy axis ratio (a proxy for morphology) is weaker in Perseus than reported in other clusters like Virgo and Coma. Furthermore, using phase-space analysis to estimate the infall times of dwarfs into the cluster, the authors find only a tentative connection between infall time and GC richness. This contrasts with clearer correlations found in Virgo, Coma, and some cosmological simulations. This discrepancy suggests that the relationship between a dwarf galaxy’s GC system and its environmental history may not be universal, but could vary from cluster to cluster depending on their specific assembly histories and intracluster conditions (e.g., tidal field strength, density of the intracluster medium).

The research demonstrates the power of modern wide-field imaging and multi-object spectroscopic surveys in advancing our understanding of GCs and dwarf galaxy evolution. It concludes that while broad trends exist, the significant scatter and cluster-to-cluster differences highlight the need for more complete observations across diverse environments and further refinement of theoretical models that can simultaneously account for internal galaxy formation processes and external environmental effects.