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 at z > 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 deg^2. In this paper, we provide an overview of the 13.6 deg^2 Southern CTIO/MOSAIC II observations. The 28.3 deg^2 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.

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