Globular clusters indicate ultra diffuse galaxies are dwarfs

TL;DR

This study analyzes the globular cluster system of the ultra-diffuse galaxy DF17 in the Coma Cluster, revealing it is consistent with a dark-matter dominated dwarf galaxy and suggesting a connection to intracluster GCs.

Contribution

It provides the first detailed analysis of DF17's globular clusters, linking its properties to dwarf galaxy characteristics and intracluster GC populations.

Findings

DF17 hosts approximately 27 globular clusters.

The GC system's properties match those of dark-matter dominated dwarf galaxies.

The GC colors suggest a connection to intracluster GCs and blue GCs in massive galaxies.

Abstract

We present an analysis of archival {\it HST/ACS} imaging in the F475W ($g_{475}$), F606W ($V_{606}$) and F814W ($I_{814}$) bands of the globular cluster (GC) system of a large (3.4 kpc effective radius) ultra-diffuse galaxy (DF17) believed located in the Coma Cluster of galaxies. We detect 11 GCs down to the 5$\sigma$ completeness limit of the imaging ($I_{814}=$27 mag). Correcting for background and our detection limits yields a total population of GCs in this galaxy of $27\pm5$ and a $V$-band specific frequency, $S_N=28\pm5$. Based on comparisons to the GC systems of Local galaxies, we show that both the absolute number and the colors of the GC system of DF17 are consistent with the GC system of a dark-matter dominated dwarf galaxy with virial mass $\sim0.9\times10^{10}$~\msun and a dark-to-stellar mass ratio, $M_{vir} / M_{ star}\sim 1000$. Based on the stellar mass-growth of the Milky Way, we show that DF17 cannot be understood as a failed Milky Way-like system, but is more similar to quenched Large Magellanic Cloud-like systems. We find that the mean color of GC population, $g_{475}-I_{814}$ = $0.91\pm0.05$ mag, coincides with the peak of the color distribution of intracluster GCs and are also similar to those of the blue GCs in the outer regions of massive galaxies. We suggest that both the intracluster GC population in Coma and the blue-peak in the GC populations of massive galaxies may be fed - at least in part - by the disrupted equivalents of systems such as DF17.