The Atacama Cosmology Telescope: Sunyaev Zel'dovich Selected Galaxy Clusters at 148 GHz in the 2008 Survey

TL;DR

This paper presents the detection of 23 galaxy clusters via the Sunyaev-Zel'dovich effect in a 2008 survey by the Atacama Cosmology Telescope, including new discoveries and analysis of their properties and detection purity.

Contribution

First blind SZ survey of galaxy clusters at 148 GHz covering 455 square degrees, with confirmation of optical counterparts and analysis of detection completeness and cluster properties.

Findings

23 clusters detected, 10 are new discoveries.

Sample purity is 100% for S/N > 6 clusters.

Sample completeness is approximately 80% for clusters above 6x10^14 solar masses.

Abstract

We report on twenty-three clusters detected blindly as Sunyaev-Zel'dovich (SZ) decrements in a 148 GHz, 455 square-degree map of the southern sky made with data from the Atacama Cosmology Telescope 2008 observing season. All SZ detections announced in this work have confirmed optical counterparts. Ten of the clusters are new discoveries. One newly discovered cluster, ACT-CL J0102-4915, with a redshift of 0.75 (photometric), has an SZ decrement comparable to the most massive systems at lower redshifts. Simulations of the cluster recovery method reproduce the sample purity measured by optical follow-up. In particular, for clusters detected with a signal-to-noise ratio greater than six, simulations are consistent with optical follow-up that demonstrated this subsample is 100% pure. The simulations further imply that the total sample is 80% complete for clusters with mass in excess of 6x10^14 solar masses referenced to the cluster volume characterized by five hundred times the critical density. The Compton y -- X-ray luminosity mass comparison for the eleven best detected clusters visually agrees with both self-similar and non-adiabatic, simulation-derived scaling laws.