Advances in Constraining Intrinsic Alignment Models with Hydrodynamic Simulations

S. Samuroff; R. Mandelbaum; J. Blazek

doi:10.1093/mnras/stab2520

paper

Advances in Constraining Intrinsic Alignment Models with Hydrodynamic Simulations

arXiv:2009.10735 · doi:10.1093/mnras/stab2520

Abstract

We use galaxies from the IllustrisTNG, MassiveBlack-II and Illustris 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 $z = 0 - 1$ . 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 galaxy-galaxy, galaxy-shape and shape-shape projected correlations, with the joint covariance matrix estimated analytically. In all of the simulations, we report non-zero 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 $\sim 2$ between redshifts $z = 0$ and $z = 1$ . We report no significant evidence for non-zero values of the tidal torquing amplitude, $A_{2}$ , in TNG, above statistical uncertainties, although MassiveBlack-II favours a moderately negative $A_{2} \sim - 2$ . 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 pixelised tidal field, alongside a proof of concept exercise using TNG. This technique is shown to be promising, although the comparison with previous results obtained via other methods is non-trivial.

arXiv comment28 pages, 18 Figures; submitted to MNRAS

Advances in Constraining Intrinsic Alignment Models with Hydrodynamic Simulations

Abstract

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