Weak Lensing by High-Redshift Clusters of Galaxies II: Mean Redshift of the Faint Background Galaxy Population

TL;DR

This study uses weak lensing measurements of high-redshift galaxy clusters to determine the average redshift of faint background galaxies, confirming consistency with photometric redshift surveys and observing shear increase with galaxy magnitude.

Contribution

It provides empirical estimates of the mean redshift of faint background galaxies through weak lensing, validating photometric redshift surveys and analyzing shear variation with magnitude.

Findings

Mean lensing redshift agrees with photometric surveys.

Detected increase in shear with galaxy magnitude.

Lensing measurements consistent with X-ray mass models.

Abstract

We use weak lensing shear measurements of six z>0.5 clusters of galaxies to derive the mean lensing redshift of the background galaxies used to measure the shear. Five of these clusters are compared to X-ray mass models and verify a mean lensing redshift for a 23<R<26.3, R-I<0.9 background galaxy population in good agreement with photometric redshift surveys of the HDF-S. The lensing strength of the six clusters is also analyzed as a function of the magnitude of the background galaxies, and an increase in shear with increasing magnitude is detected at moderate significance. The change in the strength of the shear is presumed to be caused by an increase in the mean redshift of the background galaxies with increasing magnitude, and the degree of change detected is also in agreement with those in photometric redshift surveys of the HDF-S.