Fifty star cluster candidates towards the Galactic bulge from VVV and Gaia

Abstract

We have extended our previous bulge GC searches following the procedures described by Minniti et al. (2017abc), adding a couple of additional steps to target more distant objects. Considering the high foreground contamination and in order to discard nearby sources, we used the matched VVV-Gaia catalogues of Kammers et al. (2019), with distances DBJ < 3 kpc (Bailer Jones 2018). Also, we rejected sources with proper motions consistent with the mean motion of the Galactic disk for the different fields. We then built red giant density maps and identified the over-densities with sizes typical for GCs. Finally, we checked the optical and near-IR color-magnitude diagrams for all individual objects, selecting the ones with red giant branches tighter than their surrounding fields. While in most targets a clear red clump is present, in a few cases there is also a concentration of RR Lyrae stars and/or a blue horizontal branch can be observed. We found fifty new candidate GCs.