Confirmation of a cluster of galaxies hidden behind the Galactic bulge using the VVV Survey

TL;DR

This study confirms a galaxy cluster behind the Milky Way using near-infrared data from the VVV Survey, revealing its member galaxies and indicating ongoing virialization despite high dust extinction.

Contribution

First near-infrared confirmation of a galaxy cluster behind the Galactic bulge using VVV survey data, identifying member galaxies and analyzing its dynamical state.

Findings

15 candidate cluster members identified near the red-sequence

Detection of a possible cD galaxy among members

Evidence of ongoing virialization process

Abstract

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. We attempt here to confirm the galaxy cluster with near-infrared imaging observations, and to characterize its central member galaxies. 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 and color-color diagrams and morphology criteria allowed us to select the galaxies among the numerous foreground sources. 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 respect to the X-ray peak emission is an indicator of that this cluster is still suffering a virialization process. 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.