Search for globular clusters associated with the Milky Way dwarf galaxies using Gaia DR2

We report the result of searching for globular clusters (GCs) around 55 Milky Way (MW) satellite dwarf galaxies within the distance of 450 kpc from the Galactic Centre except for the Large and Small Magellanic Clouds and the Sagittarius dwarf. For each dwarf, we analyse the stellar distribution of sources in Gaia DR2, selected by magnitude, proper motion, and source morphology. Using the kernel density estimation of stellar number counts, we identify 11 possible GC candidates. Cross-matched with existing imaging data, all 11 objects are known either GCs or galaxies and only Fornax GC 1-6 among them are associated with the targeted dwarf galaxy. Using simulated GCs, we calculate the GC detection limit M-V(lim) that spans the range from M-V(lim) similar to -7 for distant dwarfs to M-V(lim) similar to 0 for nearby systems. Assuming a Gaussian GC luminosity function, we compute that the completeness of the GC search is above 90 per cent for most dwarf galaxies. We construct the 90 per cent credible intervals/upper limits on the GC specific frequency S-N of the M-W dwarf galaxies: 12 < S-N < 47 for Fornax, S-N < 20 for the dwarfs with -12 < M-V < -10, S-N < 30 for the dwarfs with -10 < M-V < -7, and S-N < 90 for the dwarfs with M-V > -7. Based on SN, we derive the probability of galaxies hosting GCs given their luminosity, finding that the probability of galaxies fainter than M-V =-9 to host GCs is lower than 0.1.

Automated summary

This study presents the results of searching for globular clusters around 55 Milky Way satellite dwarf galaxies within 450 kpc from the Galactic Centre. The research identifies 11 possible GC candidates and calculates the GC detection limit based on simulated GCs. The study also derives the probability of galaxies hosting GCs given their luminosity, showing that galaxies fainter than M-V =-9 have a lower probability of hosting GCs.