Subaru Weak Lensing survey -- II: Multi-object Spectroscopy and Cluster Masses

TL;DR

This study uses multi-object spectroscopy to confirm weak lensing detected galaxy clusters, measures their redshifts, and compares their mass estimates with other selection methods, finding consistency across techniques.

Contribution

First spectroscopic follow-up of weak lensing cluster candidates, establishing their redshifts and validating mass estimates against optical and X-ray selected samples.

Findings

28 out of 36 candidates confirmed as clusters

Weak lensing mass correlates with galaxy velocity dispersion

No significant bias found compared to other selection methods

Abstract

We present the first results of a MOS campaign to follow up cluster candidates located via weak lensing. Our main goals are to search for spatial concentrations of galaxies that are plausible optical counterparts of the weak lensing signals, and to determine the cluster redshifts from those of member galaxies. Around each of 36 targeted cluster candidates, we obtain 15-32 galaxy redshifts. For 28 of these targets, we confirm a secure cluster identification. This includes three cases where two clusters at different redshifts are projected along the same line-of-sight. In 6 of the 8 unconfirmed targets, we find multiple small galaxy concentrations at different redshifts. In both the remaining two targets, a single small galaxy concentration is found. We evaluate the weak lensing mass of confirmed clusters. For a subsample of our most cleanly measured clusters, we investigate the statistical relation between their weak lensing mass and the velocity dispersion of their member galaxies, comparing our sample with optically and X-ray selected samples from the literature. Our lensing-selected clusters are consistent with sigma_v=sigma_sis, with a similar scatter to the optically and X-ray selected clusters. We thus find no evidence of selection bias compared to these other techniques. We also derive an empirical relation between the cluster mass and the galaxy velocity dispersion, which is in reasonable agreement with the prediction of N-body simulations in the LCDM cosmology.