Advances in constraining intrinsic alignment models with hydrodynamic simulations
Abstract
We use galaxies from the ILLUSTRISTNG, MASSIVEBLACKII, and ILLUSTRIS1 hydrodynamic simulations to investigate the behaviour of large scale galaxy intrinsic alignments. Our analysis spans four redshift slices over the approximate range of contemporary lensing surveys z = 01. We construct comparable weighted samples from the three simulations, which we then analyse using an alignment model that includes both linear and quadratic alignment contributions. Our data vector includes galaxygalaxy, galaxyshape, and shapeshape projected correlations, with the joint covariance matrix estimated analytically. In all of the simulations, we report nonzero IAs at the level of several σ. For a fixed lower mass threshold, we find a relatively strong redshift dependence in all three simulations, with the linear IA amplitude increasing by a factor of ~2 between redshifts z = 0 and z = 1. We report no significant evidence for nonzero values of the tidal torquing amplitude, A_{2}, in TNG, above statistical uncertainties, although MBII favours a moderately negative A_{2} ~ 2. Examining the properties of the TATT model as a function of colour, luminosity and galaxy type (satellite or central), our findings are consistent with the most recent measurements on real data. We also outline a novel method for constraining the TATT model parameters directly from the pixelized tidal field, alongside a proofofconcept exercise using TNG. This technique is shown to be promising, although comparison with previous results obtained via other methods is nontrivial.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 November 2021
 DOI:
 10.1093/mnras/stab2520
 arXiv:
 arXiv:2009.10735
 Bibcode:
 2021MNRAS.508..637S
 Keywords:

 gravitational lensing: weak;
 methods: numerical;
 largescale structure of Universe;
 cosmology: theory;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 28 pages, 18 Figures