Confirmation of a galaxy cluster hidden behind the Galactic bulge using the VVV survey

Context. Suzaku and Chandra X-ray observations detected a new cluster of galaxies, Suzaku J1759-3450, at a redshift z = 0.13. It is located behind the Milky Way, and the high Galactic dust extinction renders it nearly invisible at optical wavelengths. Aims. We attempt here to confirm the galaxy cluster with near-infrared imaging observations and to characterize its central member galaxies. Methods. Images from the VVV survey were used to detect candidate member galaxies of Suzaku J1759-3450 within the central region of the cluster up to 350 kpc from the X-ray peak emission. Color-magnitude diagrams, color-color diagrams, and morphology criteria allowed us to select the galaxies among the numerous foreground sources. Results. Fifteen candidate cluster members were found very close to a modeled red-sequence at the redshift of the cluster. Five members are extremely bright, and one is possibly a cD galaxy. The asymmetry in the spatial distribution of the galaxies with respect to the X-ray peak emission is an indicator that this cluster is still suffering a virialization process. Conclusions. Our investigation of Suzaku J1759-3450 demonstrates the potential of the VVV survey to study the hidden population of galaxies in the zone of avoidance.