The stellar cluster GLIMPSE-C01 is a dense stellar system located in the Galactic Plane .
Though often referred to in the literature as an old globular cluster traversing the Galactic disk , previous observations do not rule out that it is an intermediate age ( less than a few Gyr ) disk-borne cluster .
Here , we present high-resolution near-infrared spectroscopy of over 50 stars in the cluster .
We find an average radial velocity is consistent with being part of the disk , and determine the cluster ’ s dynamical mass to be ( 8 \pm 3 ) \times 10 ^ { 4 } M _ { \normalsize \odot } .
Analysis of the cluster ’ s M / L ratio , the location of the Red Clump , and an extremely high stellar density , all suggest an age of 400-800Myr for GLIMPSE-C01 , much lower than for a typical globular cluster .
This evidence therefore leads us to conclude that GLIMPSE-C01 is part of the disk population , and is the most massive Galactic intermediate-age cluster discovered to date .