The Atacama Cosmology Telescope: The Two-Season ACTPol Sunyaev-Zel'dovich Effect Selected Cluster Catalog

Abstract

We present a catalog of 182 galaxy clusters detected through the Sunyaev-Zel'dovich effect by the Atacama Cosmology Telescope in a contiguous 987.5 deg${}^2$ field. The clusters were detected as SZ decrements by applying a matched filter to 148 GHz maps that combine the original ACT equatorial survey with data from the first two observing seasons using the ACTPol receiver. Optical/IR confirmation and redshift measurements come from a combination of large public surveys and our own follow-up observations. Where necessary, we measured photometric redshifts for clusters using a pipeline that achieves accuracy $\hat{I}”z/(1+z)=0.015$ when tested on SDSS data. Under the assumption that clusters can be described by the so-called Universal Pressure Profile and its associated mass-scaling law, the full signal-to-noise > 4 sample spans the mass range $1.6<M_{500c}^{\mathrm{UPP}}/10^{14}{\mathrm{M}}_{\odot }<9.1$, with median $M_{500c}^{\mathrm{UPP}}=3.1\times 10^{14}$ M${}_{\odot }$. The sample covers the redshift range $0.1<z<1.4$ (median $z=0.49$) and 28 clusters are new discoveries (median $z=0.80$). We compare our catalog with other overlapping cluster samples selected using the SZ, optical,and X-ray wavelengths. We find the ratio of the UPP-based SZ mass to richness-based weak-lensing mass is $⟨M_{500c}^{\mathrm{UPP}}⟩/⟨M_{500c}^{\hat{\mathrm{I}}»\mathrm{WL}}⟩=0.68\pm 0.11$. After applying this calibration, the mass distribution for clusters with $M_{500c}>4\times 10^{14}$ M${}_{\odot }$ is consistent with the number of such clusters found in the South Pole Telescope SZ survey.

Accepted for publication in ApJS; 38 pages, 31 figures; a .fits table that combines tables A1-A3 is available from https://acru.ukzn.ac.za/~mjh/ACTPol_E-D56Catalog (and will be posted on LAMBDA soon)