Spectroscopic Confirmation of a Massive Red-Sequence-Selected Galaxy Cluster at z = 1.34 in the SpARCS-South Cluster Survey

TL;DR

This paper reports the spectroscopic confirmation of a massive galaxy cluster at redshift 1.34 discovered through the SpARCS survey, demonstrating the effectiveness of infrared red-sequence techniques for high-redshift cluster detection.

Contribution

It provides the first spectroscopic confirmation of a z > 1 galaxy cluster identified via the red-sequence method, showcasing the survey's capability.

Findings

Confirmed a galaxy cluster at z=1.34 with spectroscopic data.

Estimated velocity dispersion of the cluster is approximately 1050 km/s.

Demonstrated the effectiveness of infrared red-sequence detection for high-redshift clusters.

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 3.6m and CTIO 4m telescopes. The survey was designed with the primary aim of detecting galaxy clusters at z >~ 1. In tandem with pre-existing 3.6um 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/MOSAICII observations. The 28.3 deg^2 Northern CFHT/MegaCam observations are summarized in a companion paper by Muzzin et al. (2008). 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. 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.