Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution

TL;DR

This study demonstrates that galaxy-galaxy(-galaxy) lensing effectively probes galaxy evolution, revealing differences between models and limitations of simple bias assumptions at small scales.

Contribution

It compares two semi-analytic galaxy formation models using lensing statistics, highlighting their differences and the potential of lensing to test galaxy evolution theories.

Findings

Both models predict similar qualitative lensing signals but differ quantitatively.

Red galaxies show stronger lensing signals than blue galaxies.

Linear bias models are insufficient for small-scale galaxy clustering analysis.

Abstract

The gravitational lensing effect provides various ways to study the mass environment of galaxies. We investigate how galaxy-galaxy(-galaxy) lensing can be used to test models of galaxy formation and evolution. We consider two semi-analytic galaxy formation models based on the Millennium Run N-body simulation: the Durham model by Bower et al. (2006) and the Garching model by Guo et al. (2011). We generate mock lensing observations for the two models, and then employ Fast Fourier Transform methods to compute second- and third-order aperture statistics in the simulated fields for various galaxy samples. We find that both models predict qualitatively similar aperture signals, but there are large quantitative differences. The Durham model predicts larger amplitudes in general. In both models, red galaxies exhibit stronger aperture signals than blue galaxies. Using these aperture measurements and assuming a linear deterministic bias model, we measure relative bias ratios of red and blue galaxy samples. We find that a linear deterministic bias is insufficient to describe the relative clustering of model galaxies below ten arcmin angular scales. Dividing galaxies into luminosity bins, the aperture signals decrease with decreasing luminosity for brighter galaxies, but increase again for fainter galaxies. This increase is likely an artifact due to too many faint satellite galaxies in massive group and cluster halos predicted by the models. Our study shows that galaxy-galaxy(-galaxy) lensing is a sensitive probe of galaxy evolution.