Tidal alignment and tidal torquing modeling for the cosmic shear three-point correlation function and mass aperture skewness

TL;DR

This paper develops a model using the TATT formalism to understand intrinsic alignment effects on the cosmic shear three-point correlation function and mass aperture skewness, highlighting the importance of higher-order effects.

Contribution

It introduces an extension to the TATT model including velocity-shear effects and compares different effective field theory approaches in the context of cosmic shear analysis.

Findings

TATT significantly affects the 3PCF triangle configurations.

Including higher-order TATT effects can dampen the 2PCF signal and boost the skewness.

Joint 2PCF+3PCF analysis with TATT helps constrain cosmology and intrinsic alignments.

Abstract

We present a model for the intrinsic alignment contamination of the shear three-point correlation function and skewness of the mass aperture statistic using the tidal alignment and tidal torquing (TATT) formalism. We compute the intrinsic alignment bispectra components in terms of the TATT model parameters. We consider two effective field theory approaches in the literature, relate them to the TATT model parameters and an extension to TATT that includes the velocity-shear (VS) parameter. We compare the impact of changing between NLA, TATT, and TATT+VS on the theoretical computation of the 3PCF using the best fit parameters and tomographic redshift distributions from Dark Energy Survey Year 3. We find that the TATT model significantly impacts the skewed triangle configurations of the 3PCF. Additionally, including the higher-order effects from TATT can introduce opposite effects on the two-point function and on the mass aperture skewness, damping the signal of the former while boosting the signal of the latter. We argue that a joint 2PCF+3PCF analysis with the TATT model can help break the degeneracy between its model parameters and provide more robust constraints on both cosmology and intrinsic alignment amplitude parameters. We show that typical values of order unity for the intrinsic alignment parameters introduce differences of around $10\%$ between NLA and TATT predictions.