Verifications of scaling relations useful for the intrinsic alignment self-calibration

TL;DR

This paper rigorously tests and confirms the accuracy and robustness of scaling relations used for intrinsic alignment self-calibration in weak lensing, using large N-body simulations.

Contribution

It provides comprehensive validation of existing scaling relations and introduces three new relations for intrinsic alignment self-calibration.

Findings

Scaling relations verified at ~1% accuracy across relevant scales.

Relations are insensitive to halo mass, ellipticity definitions, photo-z errors, and galaxy-halo misalignments.

Three new scaling relations for B-mode intrinsic alignments are confirmed.

Abstract

The galaxy intrinsic alignment (IA) is a major challenge of weak lensing cosmology. To alleviate this problem, Zhang (2010, MNRAS, 406, L95) proposed a self-calibration method, independent of IA modeling. This proposal relies on several scaling relations between two-point clustering of IA and matter/galaxy fields, which were previously only tested with analytical IA models. In this paper, these relations are tested comprehensively with an $N$-body simulation of $3072^3$ simulation particles and boxsize 600 $h^{-1} \, \mathrm{Mpc}$. They are verified at the accuracy level of $\mathcal{O}(1)\%$ over angular scales and source redshifts of interest. We further confirm that these scaling relations are generic, insensitive to halo mass, weighting in defining halo ellipticities, photo-$z$ error, and misalignment between galaxy ellipticities and halo ellipticities. We also present and verify three new scaling relations on the B-mode IA. These results consolidate and complete the theory side of the proposed self-calibration technique.