Effects of galaxy intrinsic alignment on weak lensing peak statistics

TL;DR

This study investigates how galaxy intrinsic alignments influence weak lensing peak statistics using large simulations, highlighting their impact on shape noise and satellite galaxy effects, which are crucial for accurate cosmological inferences.

Contribution

The paper introduces a detailed simulation-based analysis of intrinsic alignment effects on weak lensing peak statistics, emphasizing satellite galaxy contributions and their dependence on redshift distribution.

Findings

Intrinsic alignments add to shape noise in peak counts.

Satellite galaxy alignments significantly influence peak signals.

Adjusting satellite IA can improve cosmological modeling.

Abstract

The galaxy intrinsic alignment (IA) is a dominant source of systematics in weak lensing (WL) studies. In this paper, by employing large simulations with semi-analytical galaxy formation, we investigate the IA effects on WL peak statistics. Different simulated source galaxy samples of different redshift distributions are constructed, where both WL shear and IA signals are included. Convergence reconstruction and peak statistics are then performed for these samples. Our results show that the IA effects on peak abundances mainly consist of two aspects. One is the additional contribution from IA to the shape noise. The other is from the satellite IA that can affect the peak signals from their host clusters significantly. The latter depends on the level of inclusion in a shear sample of the satellite galaxies of the clusters that contribute to WL peaks, and thus is sensitive to the redshift distribution of source galaxies. We pay particular attention to satellite IA and adjust it artificially in the simulations to analyze the dependence of the satellite IA impacts on its strength. This information can potentially be incorporated into the modeling of WL peak abundances, especially for high peaks physically originated from massive clusters of galaxies, and thus to mitigate the IA systematics on the cosmological constraints derived from WL peaks.