Weak lensing ( WL ) measurements suffer from well-known shear estimation biases , which can be partially corrected for with the use of image simulations .
In this work we present an analysis of simulated images that mimic Hubble Space telescope/Advance Camera for Surveys ( HST/ACS ) observations of high-redshift galaxy clusters , including cluster specific issues such as non-weak shear and increased blending .
Our synthetic galaxies have been generated to have similar observed properties as the background-selected source samples studied in the real images .
First , we used simulations with galaxies placed on a grid to determine a revised signal-to-noise-dependent ( S / N _ { \mathrm { KSB } } ) correction for multiplicative shear measurement bias , and to quantify the sensitivity of our KSB+ bias calibration to mismatches of galaxy or PSF properties between the real data and the simulations .
Next , we studied the impact of increased blending and light contamination from cluster and foreground galaxies , finding it to be negligible for high-redshift ( z > 0.7 ) clusters , whereas shear measurements can be affected at the \sim 1 \% level for lower redshift clusters given their brighter member galaxies .
Finally , we studied the impact of fainter neighbours and selection bias using a set of simulated images that mimic the positions and magnitudes of galaxies in Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey ( CANDELS ) data , thereby including realistic clustering .
While the initial SExtractor object detection causes a multiplicative shear selection bias of -0.028 \pm 0.002 , this is reduced to -0.016 \pm 0.002 by further cuts applied in our pipeline .
Given the limited depth of the CANDELS data , we compared our CANDELS-based estimate for the impact of faint neighbours on the multiplicative shear measurement bias to a grid-based analysis , to which we added clustered galaxies to even fainter magnitudes based on Hubble Ultra Deep Field ( HUDF ) data , yielding a refined estimate of \sim - 0.013 .
Our sensitivity analysis suggests that our pipeline is calibrated to an accuracy of \sim 0.015 once all corrections are applied , which is fully sufficient for current and near-future weak lensing studies of high-redshift clusters .
As an application , we used it for a refined analysis of three highly relaxed clusters from the South Pole Telescope Sunyaev-Zeldovich ( SPT-SZ ) survey , where we now included measurements down to the cluster core ( r > 200 kpc ) as enabled by our work .
Compared to previously employed scales ( r > 500 kpc ) , this tightens the cluster mass constraints by a factor 1.38 on average .