Projection effects of large-scale structures on weak-lensing peak abundances

TL;DR

This paper investigates how large-scale structures along lines of sight influence weak-lensing peak counts, showing their significance for future surveys and proposing an improved model to account for these effects in cosmological analyses.

Contribution

The authors extend an existing weak-lensing peak model by incorporating large-scale structure projection effects, improving accuracy for future high-redshift surveys.

Findings

LSS effects are negligible for current surveys with high shape noise.

LSS effects become significant for future surveys with median redshift around 1.

Incorporating LSS effects reduces biases in cosmological parameter estimation.

Abstract

High peaks in weak lensing (WL) maps originate dominantly from the lensing effects of single massive halos. Their abundance is therefore closely related to the halo mass function and thus a powerful cosmological probe. On the other hand, however, besides individual massive halos, large-scale structures (LSS) along lines of sight also contribute to the peak signals. In this paper, with ray tracing simulations, we investigate the LSS projection effects. We show that for current surveys with a large shape noise, the stochastic LSS effects are subdominant. For future WL surveys with source galaxies having a median redshift $z_{\mathrm{med}}\sim1$ or higher, however, they are significant. For the cosmological constraints derived from observed WL high peak counts, severe biases can occur if the LSS effects are not taken into account properly. We extend the model of \citet{Fan2010} by incorporating the LSS projection effects into the theoretical considerations. By comparing with simulation results, we demonstrate the good performance of the improved model and its applicability in cosmological studies.