Candidate Star Clusters Toward The Inner Milky Way Discovered On Deep-Stacked K-S-Band Images From The Vvv Survey

The census of star clusters in the inner Milky Way is incomplete because of\nextinction and crowding. We embarked on a program to expand the star cluster\nlist in the direction of the inner Milky Way using deep stacks of Ks-band\nimages from the VISTA Variables in Via Lactea (VVV) Survey. We applied an\nautomated two-step procedure to the point-source catalog derived from the deep\nKs images: first, we identified overdensities of stars, and then we selected\nonly candidate clusters with probable member stars that match an isochrone with\na certain age, distance, and extinction on the color-magnitude diagram. This\npilot project only investigates the cluster population in part of one VVV tile,\nthat is, b201. We identified nine cluster candidates and estimated their\nparameters. The new candidates are compact with a typical radius on the sky of\n~0.2--0.4 arcmin (~0.4-1.6 pc at their estimated distances). They are located\nat distances of ~5-14 kpc from the Sun and are subject to moderate extinction\nof E(B-V)=0.4-1.0 mag. They are sparse, probably evolved, with typical ages\nlog(t/1 yr)~9. Based on the locations of the objects inside the Milky Way, we\nconclude that one of these objects is probably associated with the disk or halo\nand the remaining objects are associated with the bulge or the halo. The\ncluster candidates reported here push the VVV Survey cluster detection to the\nlimit. These new objects demonstrate that the VVV survey has the potential to\nidentify thousands of additional cluster candidates. The sub-arcsec angular\nresolution nd the near-infrared wavelength regimen give it a critical advantage\nover other surveys.\n