Intrinsic alignments of the extended radio continuum emission of galaxies in the EAGLE simulations

Abstract

We present measurements of the intrinsic alignments (IAs) of the star-forming gas of galaxies in the EAGLE simulations. Radio continuum imaging of this gas enables cosmic shear measurements complementary to optical surveys. We measure the orientation of star-forming gas with respect to the direction to, and orientation of, neighbouring galaxies. Star-forming gas exhibits a preferentially radial orientation-direction alignment that is a decreasing function of galaxy pair separation, but remains significant to $\gtrsim 1$ Mpc at $z=0$. The alignment is qualitatively similar to that exhibited by the stars, but is weaker at fixed separation. Pairs of galaxies hosted by more massive subhaloes exhibit stronger alignment at fixed separation, but the strong alignment of close pairs is dominated by $\sim L^{\star }$ galaxies and their satellites. At fixed comoving separation, the radial alignment is stronger at higher redshift. The orientation-orientation alignment is consistent with random at all separations, despite subhaloes exhibiting preferential parallel minor axis alignment. The weaker IA of star-forming gas than for stars stems from the former's tendency to be less well aligned with the dark matter structure of galaxies than the latter, and implies that the systematic uncertainty due to IA may be less severe in radio continuum weak lensing surveys than in optical counterparts. Alignment models equating the orientation of star-forming gas discs to that of stellar discs or the DM structure of host subhaloes will therefore overestimate the impact of IAs on radio continuum cosmic shear measurements.

18 pages, 13 figures. Paper submitted to MNRAS

References in corpus (31)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
• The effect of photo-ionization on the cooling rates of enriched, astrophysical plasmas
• KiDS-1000 Cosmology: Multi-probe weak gravitational lensing and spectroscopic galaxy clustering constraints
• Chemical enrichment in cosmological, smoothed particle hydrodynamics simulations
• Dark energy constraints from cosmic shear power spectra: impact of intrinsic alignments on photometric redshift requirements
• Dark Energy Survey Year 3 Results: Cosmology from Cosmic Shear and Robustness to Data Calibration
• Dark Energy Survey Year 3 Results: Cosmology from Cosmic Shear and Robustness to Modeling Uncertainty
• Modelling discontinuities and Kelvin-Helmholtz instabilities in SPH
• Baryon effects on the internal structure of LCDM halos in the EAGLE simulations
• Inviscid SPH
• The Intrinsic Alignment of Galaxies and its Impact on Weak Gravitational Lensing in an Era of Precision Cosmology
• Constraints on intrinsic alignment contamination of weak lensing surveys using the MegaZ-LRG sample
• Intrinsic alignments of SDSS-III BOSS LOWZ sample galaxies
• Potential sources of contamination to weak lensing measurements: constraints from N-body simulations
• Galaxy Cold Gas Contents in Modern Cosmological Hydrodynamic Simulations
• The halo model as a versatile tool to predict intrinsic alignments
• Intrinsic alignment of simulated galaxies in the cosmic web: implications for weak lensing surveys
• Energy equipartition between stellar and dark matter particles in cosmological simulations results in spurious growth of galaxy sizes
• An EFT description of galaxy intrinsic alignments
• Intrinsic alignments of galaxies in the MassiveBlack-II simulation: analysis of two-point statistics
• The build up of the correlation between halo spin and the large scale structure
• Advances in Constraining Intrinsic Alignment Models with Hydrodynamic Simulations
• A Technique for Weak Lensing with Velocity Maps: Eliminating Ellipticity Noise in HI Radio Observations
• Power Spectrum of Intrinsic Alignments of Galaxies in IllustrisTNG
• SuperCLASS -- III. Weak lensing from radio and optical observations in Data Release 1
• Radio-Optical Galaxy Shape Correlations in the COSMOS Field
• The impact of Self-Interacting Dark Matter on the Intrinsic Alignments of Galaxies
• The morphology of star-forming gas and its alignment with galaxies and dark matter haloes in the EAGLE simulations
• SuperCLASS -- I. The Super CLuster Assisted Shear Survey: Project overview and Data Release 1
• SuperCLASS -- II: Photometric Redshifts and Characteristics of Spatially-Resolved $\mu$Jy Radio Sources

Cited by in corpus (3)

• Intrinsic alignments of bulges and discs
• A rising tide: Intrinsic alignments since the turn of the millennium
• First Light And Reionisation Epoch Simulations (FLARES) XVI: Size Evolution of Massive Dusty Galaxies at Cosmic Dawn from UV to IR