Spectroscopic confirmation of a massive red-sequence-selected galaxy cluster at Z = 1.34 in the SpARCS-south cluster survey

Abstract

The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a z′-passband imaging survey, consisting of deep (z′ ≃ 24 AB) observations made from both hemispheres using the CFHT 3.6 m and CTIO 4 m telescopes. The survey was designed with the primary aim of detecting galaxy clusters atz > 1. In tandem with pre-existing 3.6 μm observations from the Spitzer Space Telescope SWIRE Legacy Survey, SpARCS detects clusters using an infrared adaptation of the two-filter red-sequence cluster technique. The total effective area of the SpARCS cluster survey is 41.9 deg2. In this paper, we provide an overview of the 13.6 deg2 Southern CTIO/MOSAIC II observations. The 28.3 deg2 Northern CFHT/MegaCam observations are summarized in a companion paper by Muzzin et al. In this paper, we also report spectroscopic confirmation of SpARCS J003550-431224, a very rich galaxy cluster at z = 1.335, discovered in the ELAIS-S1 field. To date, this is the highest spectroscopically confirmed redshift for a galaxy cluster discovered using the red-sequence technique. Based on nine confirmed members, SpARCS J003550-431224 has a preliminary velocity dispersion of 1050 ± 230 km s-1. With its proven capability for efficient cluster detection, SpARCS is a demonstration that we have entered an era of large, homogeneously selected z > 1 cluster surveys.