Weak-lensing Shear-Selected Galaxy Clusters from the Hyper Suprime-Cam Subaru Strategic Program: III. A precision cosmological sample enabled by optical confirmation

I-Non Chiu; Kai-Feng Chen; Masamune Oguri; Satoshi Miyazaki; Surhud More; Atsushi J. Nishizawa; Nobuhiro Okabe; Ken Osato; Naomi Ota; Tomomi Sunayama; Sut-Ieng Tam; Keiichi Umetsu

arXiv · 2608.02755

Weak-lensing Shear-Selected Galaxy Clusters from the Hyper Suprime-Cam Subaru Strategic Program: III. A precision cosmological sample enabled by optical confirmation

I-Non Chiu·Kai-Feng Chen·Masamune Oguri·Satoshi Miyazaki·Surhud More·Atsushi J. Nishizawa·Nobuhiro Okabe·Ken Osato·Naomi Ota·Tomomi Sunayama·Sut-Ieng Tam·Keiichi Umetsu

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Abstract

We develop fCAMIRA (forced-mode CAMIRA), a tool for optical cluster confirmation, and apply it to a sample of 129 weak-lensing (WL) shear-selected galaxy clusters identified in aperture-mass maps obtained from the Hyper Suprime-Cam Subaru Strategic Program Three-Year (HSC-SSP Y3) weak-lensing data. fCAMIRA is built upon the CAMIRA cluster-finding algorithm and relies on a red-sequence (RS) galaxy model that is calibrated in a data-driven way. The RS model adopts the metallicity-luminosity relation measured in this work using X-ray-selected clusters up to redshift $z\approx1.3$, followed by the calibration of color offsets using large spectroscopic samples. With the RS model, we build two types of galaxy richness maps, one obtained with a spatial filter matched to a typical cluster size of $R=0.8\,h^{-1}\,\mathrm{Mpc}$ and the other obtained with a fixed angular-size filter identical to that used in constructing the WL aperture-mass maps. The fCAMIRA algorithm utilizes these two richness maps, identifies all optical counterpart candidates along the line of sight of each shear-selected cluster, and measures the cluster photometric redshift from the highest-ranked counterpart. The ranking is determined by the fractional lensing contribution $f_{\mathrm{lens}}$ of each candidate. Using available spectroscopic cluster redshifts, we quantify the mean bias and scatter in the cluster photometric redshifts at levels of approximately 0.005 and 0.008, respectively, demonstrating excellent photometric-redshift performance. We compare the fCAMIRA photometric redshifts with estimates from direct positional cross-matching and find that approximately 8% of the total sample exhibits redshift discrepancies greater than 0.15. This outlier fraction is primarily attributed to projection effects, leading to the misidentification of the optical counterparts. (abridged)

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I-Non Chiu, Kai-Feng Chen, Masamune Oguri, Satoshi Miyazaki, Surhud More, Atsushi J. Nishizawa, Nobuhiro Okabe, Ken Osato, Naomi Ota, Tomomi Sunayama, Sut-Ieng Tam, Keiichi Umetsu. 2026-08-03. Weak-lensing Shear-Selected Galaxy Clusters from the Hyper Suprime-Cam Subaru Strategic Program: III. A precision cosmological sample enabled by optical confirmation. https://arxiv.org/abs/2608.02755

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