A new low-luminosity globular cluster discovered in the Milky Way with
  the VVVX survey
  The VISTA Variables in the Via L\'actea Extended Survey (VVVX) allows probing
previously unexplored regions of the inner Milky Way (MW). We are looking for
new candidate globular clusters (GCs), with the aim of completing the census of
the MW GC system. We searched and characterised new GCs, using a combination of
the near-IR VVVX survey and 2MASS datasets, and the optical Gaia EDR3
photometry and its precise proper motions (PMs). We report the discovery of a
new Galactic GC, named Garro 02, situated at RA=18:05:51.1, Dec=-17:42:02 and
l=12.042 deg, b=+1.656 deg. Performing a PM-decontamination procedure, we built
a final catalogue with all cluster members, on which we performed a photometric
analysis. We calculated a reddening of $E(J-K_s)=1.07\pm 0.06$ mag and
extinction of $A_{Ks}=0.79\pm 0.04$ mag in the near-IR; while $E(BP-RP)=2.40\pm
0.01$ mag and $A_{G}=4.80\pm 0.02$ mag in optical passbands. Its heliocentric
distance is $D=5.6\pm 0.8$ kpc, which places Garro 02 at a Galactocentric
distance of $R_G=2.9$ kpc and Z=0.006 kpc above the Galactic plane. We
estimated the metallicity and age by comparison with known GCs and by fitting
PARSEC isochrones, finding [Fe/H]$=-1.30\pm 0.2$ dex and age=$12\pm 2$ Gyr. We
derived the mean cluster PM of $(\mu_{\alpha}^{\ast}, \mu_{\delta}) = (-6.07\pm
0.62, -6.15\pm 0.75)$ mas yr$^{-1}$. We calculated the cluster luminosity in
the near-IR of $M_{Ks}=-7.52\pm 1.23$ mag, which is equivalent to $M_{V}=-5.44$
mag. The core and tidal radii from the radial density profile are $r_c =1.25\pm
0.27$ arcmin (2.07 pc) and $r_t = 7.13\pm 3.83$ arcmin (11.82 pc),
respectively. We confirm Garro 02 as a new genuine Galactic GC, located in the
MW bulge. It is a low-luminosity, metal-poor, and old GC, and it is a lucky
survivor of the strong dynamical processes that occurred during the MW's entire
life.
