Lensing Magnification: A novel method to weigh high-redshift clusters and its application to SpARCS

TL;DR

This paper presents a new weak lensing magnification method using high-redshift background galaxies to measure galaxy cluster masses at z>1, enabling efficient calibration of mass-observable relations for cosmology.

Contribution

The novel method utilizes Lyman-break galaxies for weak lensing magnification to measure high-redshift cluster masses, validated with current data and promising for future large surveys.

Findings

Detected magnification signal at >3-sigma level with current data

Mass estimates from magnification agree with richness-based estimates

Method shows robustness against systematic effects

Abstract

We introduce a novel method to measure the masses of galaxy clusters at high redshift selected from optical and IR Spitzer data via the red-sequence technique. Lyman-break galaxies are used as a well understood, high-redshift background sample allowing mass measurements of lenses at unprecedented high redshifts using weak lensing magnification. By stacking a significant number of clusters at different redshifts with average masses of ~1-3x10^14M_sun, as estimated from their richness, we can calibrate the normalisation of the mass-richness relation. With the current data set (area: 6 deg^2) we detect a magnification signal at the >3-sigma level. There is good agreement between the masses estimated from the richness of the clusters and the average masses estimated from magnification, albeit with large uncertainties. We perform tests that suggest the absence of strong systematic effects and support the robustness of the measurement. This method - when applied to larger data sets in the future - will yield an accurate calibration of the mass-observable relations at z>~1 which will represent an invaluable input for cosmological studies using the galaxy cluster mass function and astrophysical studies of cluster formation. Furthermore this method will probably be the least expensive way to measure masses of large numbers of z>1 clusters detected in future IR-imaging surveys.