A large sample of shear selected clusters from the Hyper Suprime-Cam Subaru Strategic Program S16A wide field mass maps

TL;DR

This study uses weak gravitational lensing to identify galaxy clusters over 160 square degrees, revealing a sample of shear-selected clusters with properties consistent with optical and X-ray data, and providing insights into their dark matter profiles.

Contribution

First large-area weak lensing survey with high-resolution mass maps identifying shear-selected galaxy clusters and analyzing their multi-wavelength properties.

Findings

65 mass map peaks with SN > 4.7 identified, 39 confirmed in optical catalogs.

Most shear-selected peaks have optical counterparts, with few false positives.

Stacked X-ray analysis shows shear-selected clusters are X-ray under-luminous compared to X-ray selected clusters.

Abstract

We present the result of searching for clusters of galaxies based on weak gravitational lensing analysis of the $\sim 160$~deg$^2$ area surveyed by Hyper Suprime-Cam (HSC) as a Subaru Strategic Program. HSC is a new prime focus optical imager with a 1.5 diameter field of view on the 8.2-meter Subaru telescope. The superb median seeing on the HSC $i$-band images of $0.56$ arcsec allows the reconstruction of high angular resolution mass maps via weak lensing, which is crucial for the weak lensing cluster search. We identify 65 mass map peaks with signal-to-noise (SN) ratio larger than 4.7, and carefully examine their properties by cross-matching the clusters with optical and X-ray cluster catalogs. We find that all the 39 peaks with SN$>5.1$ have counterparts in the optical cluster catalogs, and only 2 out of the 65 peaks are probably false positives. The upper limits of X-ray luminosities from ROSAT All Sky Survey (RASS) imply the existence of an X-ray under-luminous cluster population. We show that the X-rays from the shear selected clusters can be statistically detected by stacking the RASS images. The inferred average X-ray luminosity is about half that of the X-ray selected clusters of the same mass. The radial profile of the dark matter distribution derived from the stacking analysis is well modeled by the Navarro-Frenk-White profile with a small concentration parameter value of $c_{500}\sim 2.5$, which suggests that the selection bias on the orientation or the internal structure for our shear selected cluster sample is not strong.