Speaker
Description
Cosmic shear is a central probe of the late-time Universe, but the interpretation of its measurements is limited by astrophysical systematics such as intrinsic alignments (IA) of galaxies. Upcoming lensing surveys will enable measurements of higher-order statistics with increased precision, providing non-Gaussian information beyond two-point correlations. Interpreting these measurements requires IA models that are accurate at higher order while remaining consistent with existing two-point constraints.
In this talk, I will present a study of the three-point IA signal measured in the FLAMINGO hydrodynamical simulation. We measure both the three-point correlation function (3PCF) and third-order aperture-mass statistics, using galaxy and halo shapes from the largest FLAMINGO simulation, ${\rm (2.8 \, Gpc)}^3$. This enables high-significance detections over a wide range of scales and triangle configurations. I will compare these measurements to predictions from the tree-level effective field theory (EFT) of IA, testing the full model, reduced variants, and co-evolution relations between model parameters. I will show that the EFT provides a good description of the measured three-point signal, with an alignment amplitude consistent with that inferred from two-point statistics. Neglecting higher-order EFT contributions can bias parameter constraints and degrade the fit, while co-evolution relations provide a simpler description that performs close to the full model, making them promising for future photometric weak-lensing analyses.
| Other topic / keywords: | Weak lensing, intrinsic alignments, large-scale structure, hydrodynamical simulations, effective field theory |
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