Pyne, Susan; Tenneti, Ananth; Joachimi, Benjamin; (2022) Three-point intrinsic alignments of dark matter haloes in the IllustrisTNG simulation. Monthly Notices of the Royal Astronomical Society , 516 (2) pp. 1829-1845. 10.1093/mnras/stac2351.

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Abstract

We use the IllustrisTNG suite of cosmological simulations to measure intrinsic alignment (IA) bispectra of dark matter subhaloes between redshifts 0 and 1. We decompose the intrinsic shear field into E- and B- modes and find that the bispectra B_{δδE} and B_{δEE}, between the matter overdensity field, δ, and the E-mode field, are detected with high significance. We also model the IA bispectra analytically using a method consistent with the two-point non-linear alignment model. We use this model and the simulation measurements to infer the IA amplitude A_{IA} and find that values of A_{IA} obtained from IA power spectra and bispectra agree well at scales up to k_{max} = 2 hMpc^{−1}⁠. For example at z = 1, A_{IA} = 2.13 ± 0.02 from the cross power spectrum between the matter overdensity and E-mode fields and A_{IA} = 2.11 ± 0.03 from B_{δδE}. This demonstrates that a single physically motivated model can jointly model two-point and three-point statistics of IAs, thus enabling a cleaner separation between IAs and cosmological weak lensing signals.

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