Globular Cluster Systems in Dwarf Galaxies: Catalogs and Comparisons

TL;DR

This paper assembles a comprehensive catalog of dwarf galaxy globular cluster systems (GCS) from seven surveys and literature sources, standardizing to total GCS mass $M_{GCS}$ and peak halo mass $M_{h,peak}$ to enable consistent comparisons. It adopts a dwarf-appropriate stellar-to-halo mass relation from $ ext{log}(M_{*}) = 10.457 - \log(10^{-2.10 x} + 10^{-0.464x}) - 0.812 \exp[-0.5(x/0.319)^2]$, with $x = \log(M_{peak}/10^{11.889})$, and converts $N_{GC}$ to $M_{GCS}$ using $\langle M_{GC} \rangle = (2.26 \times 10^4) M_{dyn}^{0.098}$. The study finds that, for $M_{*} \lesssim 5 \times 10^9\,M_\odot$, the $M_{GCS}-M_h$ relation remains approximately linear, but UDGs and ESLBGs show systematically higher GC specific frequencies and lie above the relation on average, driving considerable scatter. By separating UDGs/ELSBGs, the authors show these populations follow distinct slopes in the $M_{GCS}-M_h$ plane, implying different formation and survival histories, while the low-mass dwarfs align with the global trend when considering peak halo mass. The work provides a publicly accessible, standardized dataset for probing dwarf galaxy assembly histories and informs whether the present-day GCS mass reflects a past peak halo mass or ongoing evolution, with implications for GC formation channels and tidal processing.

Abstract

The connection between a galaxy's total globular cluster system (GCS) mass and its halo mass has been studied for decades and it has been found that galaxies at nearly all observed masses adhere to a linear scaling relation between these properties. However, while we have ample, homogeneous data for galaxies with halo masses $M_h \gtrsim 10^{10} M_{\odot}$ the data available for low-mass galaxies is more sparse, and both GCS mass and halo mass estimates are determined using varying methodologies. This work compiles all available literature data for dwarf galaxies with confident stellar mass and GC count estimates, and converts these estimates to GCS masses and peak halo masses using a standard conversion. This allows for a consistent comparison of these masses to be made and a complete study of the behaviour of the $M_{GCS}-M_h$ relation to be conducted. We compare the positions of classical dwarfs on the scaling relation to that of ultra diffuse galaxies and extremely low-surface brightness galaxies and find that these non-classical dwarfs have, on average, systematically higher GC specific frequencies. This also makes them, on average, systematically positively offset from the $M_{GCS}-M_h$ relation, driving much of the high-$M_{GCS}$ scatter observed.

Figures (4)

• Figure 1: Left:$N_{GC}$ vs host galaxy total stellar mass for all galaxies in the combined sample and the more massive galaxies in the Virgo Cluster Catalog Peng08 and the BCGs in the Dornan25 sample. Right: Same as the left panel, but with stellar masses now converted to peak halo masses following the method outlines in Section \ref{['sec:masses']}.
• Figure 2: Left:$M_{GCS}$ vs peak $M_{h}$ for all galaxies in the combined sample and the more massive galaxies in the Virgo Cluster Catalog Peng08 and the BCGs in the Dornan25 sample. Right: Same as the left panel, but zoomed-in on the combined dwarf galaxy catalog only.
• Figure 3: $M_{GCS}$ vs peak $M_{h}$ for all galaxies in the combined sample. Orange triangles represent classical dwarfs, purple squares represent UDGs, and blue triangles represent ESLBGs ($\mu_{g,0}>27$). The black dashed line is the global $M_{GCS}$ vs peak $M_{h}$ relation fit, determined including massive galaxies. The blue line is the relation fit for only the dwarf galaxies in this combined catalog, and the red line is the relation fit for only UDGs and ELSBGs. The exact fits for these lines can be found in table \ref{['tab:ch3_fits']}
• Figure 4: GC specifc mass frequency plotted against stellar mass for the combined dwarf galaxy catalog plus the massive Virgo cluster galaxies and the BCG sample. UDGs and ELSBGs are denoted by stars and triangles respectively. The fit for all dwarfs is plotted in black, the fit for UDGs only is plotted in purple, and the fit for ESLBGs only is plotted in orange.The exact fits for these lines can be found in table \ref{['tab:specific']}