Confirmation and physical characterization of the new bulge globular
  cluster Patchick 99 from the VVV and Gaia surveys
  Globular clusters (GCs) are important tools to understand the formation and
evolution of the Milky Way (MW). The known MW sample is still incomplete, so
the discovery of new GC candidates and the confirmation of their nature are
crucial for the census of the MW GC system. Our goal is to confirm the physical
nature of two GC candidates: Patchick99 and TBJ3, located towards the Galactic
bulge. We use public data in the near-IR from the VVV, VVVX and 2MASS along the
with deep optical data from the Gaia DR2, in order to estimate their main
physical parameters: reddening, extinction, distance, luminosity, mean cluster
proper motions (PMs), size, metallicity and age. We investigate both candidates
at different wavelengths. We use near-IR and optical CMDs in order to analyse
Patchick99. We decontaminate CMDs following a statistical procedure and
PM-selection. Reddening and extinction are derived by adopting reddening maps.
Metallicity and age are evaluated by fitting stellar isochrones. Reddening and
extinction are E(J-Ks)=0.12+/-0.02 mag, AKs=0.09+/-0.01 mag from the VVV data,
whereas E(BP-RP)=0.21+/-0.03 mag, AG=0.68+/-0.08 mag from Gaia DR2. We estimate
a distance d=6.4+/-0.2 kpc in near-IR and D=7.0+/-0.2 kpc in optical. We derive
its metallicity and age fitting PARSEC isochrones, finding [Fe/H]=-0.2+/-0.2
dex and t=10+/-2 Gyr. The mean PMs for Patchick99 are pmRA=-298+/-1.74 mas/yr
and pmDEC=-5.49+/-2.02 mas/yr. We confirm that it is a low-luminosity GC, with
MKs=-7.0+/-0.6 mag. The radius estimation is performed building the radial
density profile, finding r~10'. We recognise 7 RR Lyrae star members within 8.2
arcmin from its centre, confirming the distance found by other methods. We
found that TBJ3 shows mid-IR emissions that are not present in GCs. We discard
TBJ3 as GC candidate and we focus on Patchick99. We conclude that it is an old
metal-rich GC, situated in the Galactic bulge.
