Testing Weak Lensing Maps With Redshift Surveys: A Subaru Field

TL;DR

This study uses a dense redshift survey to evaluate the accuracy of weak lensing maps in identifying massive halos, confirming that most high signal-to-noise peaks correspond to real structures and improving detection methods.

Contribution

It provides a detailed assessment of the completeness and purity of weak lensing peak identification using redshift surveys, demonstrating improved detection techniques with better imaging data.

Findings

Two-thirds of high S/N peaks correspond to massive systems

Better seeing enables detection of less massive halos

Improved peak removal enhances map and survey agreement

Abstract

We use a dense redshift survey in the foreground of the Subaru GTO2deg^2 weak lensing field (centered at $\alpha_{2000}$ = 16$^h04^m44^s$;$\delta_{2000}$ =43^\circ11^{\prime}24^{\prime\prime}$) to assess the completeness and comment on the purity of massive halo identification in the weak lensing map. The redshift survey (published here) includes 4541 galaxies; 4405 are new redshifts measured with the Hectospec on the MMT. Among the weak lensing peaks with a signal-to-noise greater that 4.25, 2/3 correspond to individual massive systems; this result is essentially identical to the Geller et al. (2010) test of the Deep Lens Survey field F2. The Subaru map, based on images in substantially better seeing than the DLS, enables detection of less massive halos at fixed redshift as expected. We demonstrate that the procedure adopted by Miyazaki et al. (2007) for removing some contaminated peaks from the weak lensing map improves agreement between the lensing map and the redshift survey in the identification of candidate massive systems.