Measuring galaxy-galaxy-galaxy-lensing with higher precision and accuracy

TL;DR

This paper introduces three methodological improvements to galaxy-galaxy-galaxy lensing measurements, significantly enhancing precision, reducing bias, and accounting for lens magnification effects, validated through simulations.

Contribution

The paper presents novel techniques for weighting, adaptive binning, and magnification correction in G3L measurements, improving accuracy and signal-to-noise ratio.

Findings

Signal-to-noise ratio increased by 35%

Bias at small scales reduced by up to 40%

Magnification contributes about 10% to the total signal

Abstract

Galaxy-galaxy-galaxy lensing (G3L) is a powerful tool for constraining the three-point correlation between the galaxy and matter distribution and thereby models of galaxy evolution. We propose three improvements to current measurements of G3L: (i) a weighting of lens galaxies according to their redshift difference, (ii) adaptive binning of the three-point correlation function, and (iii) accounting for the effect of lens magnification by the cosmic large-scale structure. Improvement (i) is designed to improve the precision of the G3L measurement, whereas improvements (ii) and (iii) remove biases of the estimator. We further show how the G3L signal can be converted from angular into physical scales. The improvements were tested on simple mock data and simulated data based on the Millennium Run with an implemented semi-analytic galaxy model. Our improvements increase the signal-to-noise ratio by 35 % on average at angular scales between 0.1 arcmin and 10 arcmin and physical scales between $0.02$ and $2 \, h^{-1}\, \textrm{Mpc}$. They also remove the bias of the G3L estimator at angular scales below 1 arcmin, which was originally up to 40 %. The signal due to lens magnification is approximately 10 % of the total signal.