The MillenniumTNG Project: Intrinsic alignments of galaxies and halos

Abstract

The intrinsic alignment (IA) of observed galaxy shapes with the underlying cosmic web is a source of contamination in weak lensing surveys. Sensitive methods to identify the IA signal will therefore need to be included in the upcoming weak lensing analysis pipelines. Hydrodynamical cosmological simulations allow us to directly measure the intrinsic ellipticities of galaxies and thus provide a powerful approach to predict and understand the IA signal. Here we employ the novel, large-volume hydrodynamical simulation MTNG740, a product of the MillenniumTNG (MTNG) project, to study the IA of galaxies. We measure the projected correlation functions between the intrinsic shape/shear of galaxies and various tracers of large-scale structure, $w_{+g},w_{+m},w_{++}$ over the radial range $r_{\mathrm{p}}\in [0.02,200]h^{-1}\mathrm{Mpc}$ and at redshifts $z=0.0$, $0.5$ and $1.0$. We detect significant signal-to-noise IA signals with the density field for both elliptical and spiral galaxies. We also find significant intrinsic shear-shear correlations for ellipticals. We further examine correlations of the intrinsic shape of galaxies with the local tidal field. Here we find a significant IA signal for elliptical galaxies assuming a linear model. We also detect a weak IA signal for spiral galaxies under a quadratic tidal torquing model. Lastly, we measure the alignment between central galaxies and their host dark-matter halos, finding small to moderate misalignments between their principal axes that decline with halo mass.

16 pages, 14 figures

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Cited by in corpus (16)

• DES Y3 + KiDS-1000: Consistent cosmology combining cosmic shear surveys
• The MillenniumTNG Project: The impact of baryons and massive neutrinos on high-resolution weak gravitational lensing convergence maps
• The MillenniumTNG Project: Semi-analytic galaxy formation models on the past lightcone
• The impact of baryons on the internal structure of dark matter haloes from dwarf galaxies to superclusters in the redshift range 0<z<7
• Evolution of central galaxy alignments in simulations
• Dark Energy Survey Year 3: Blue Shear
• Investigating the galaxy-halo connection of DESI Emission-Line Galaxies with SHAMe-SF
• Intrinsic galaxy alignments in the KiDS-1000 bright sample: dependence on colour, luminosity, morphology, and galaxy scale
• A rising tide: Intrinsic alignments since the turn of the millennium
• Probabilistic Estimators of Lagrangian Shape Biases: Universal Relations and Physical Insights
• The relation of galaxies and dark matter haloes to the filamentary cosmic web
• Differences in baryonic and dark matter scaling relations of galaxy clusters: A comparison between IllustrisTNG simulations and observations
• Parity Violation in Galaxy Shapes: Primordial Non-Gaussianity
• Non-linear infusion of intrinsic alignment and source clustering: impact on non-Gaussian cosmic shear statistics
• Estimating the triaxiality of massive clusters from 2D observables in MillenniumTNG with machine learning
• Intrinsic alignments of galaxies in multiple projections