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

¹ Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
e-mail: georginacoldwell@gmail.com
² Departamento de Geofísica y Astronomía – Facultad de Ciencias Exactas, Físicas y Naturales – Universidad Nacional de San Juan, San Juan, Argentina
³ Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
⁴ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile
⁵ Vatican Observatory, 00120 Vatican City State, Italy
⁶ Departamento de Ciencias Físicas, Universidad Andrés Bello, República 220, Santiago, Chile

Received: 19 January 2014
Accepted: 30 June 2014

Abstract

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.