Power spectrum of halo intrinsic alignments in simulations
Abstract
We use a suite of Nbody simulations to study intrinsic alignments (IA) of halo shapes with the surrounding largescale structure in the ΛCDM model. For this purpose, we develop a novel method to measure multipole moments of the threedimensional power spectrum of the Emode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$ ), and those of the autopower spectrum of the Emode, $P^{(\ell)}_{EE}(k)$ , based on the E/Bmode decomposition. The IA power spectra have nonvanishing amplitudes over the linear to nonlinear scales, and the largescale amplitudes at k ≲ 0.1 h^{1} Mpc are related to the matter power spectrum via a constant coefficient (A_{IA}), similar to the linear bias parameter of galaxy or halo density field. We find that the cross and autopower spectra P_{δE} and P_{EE} at nonlinear scales, k ≳ 0.1 h^{1} Mpc, show different kdependences relative to the matter power spectrum, suggesting a violation of the nonlinear alignment model commonly used to model contaminations of cosmic shear signals. The IA power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts, and cosmological parameters (Ω_{m}, S_{8}). The cumulative signaltonoise ratio for the IA power spectra is about 60 per cent of that for the halo density power spectrum, where the supersample covariance is found to give a significant contribution to the total covariance. Thus our results demonstrate that the IA power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be used to probe the underlying matter power spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density power spectrum.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 February 2021
 DOI:
 10.1093/mnras/staa3625
 arXiv:
 arXiv:2004.12579
 Bibcode:
 2021MNRAS.501..833K
 Keywords:

 cosmology: theory;
 largescale structure of Universe;
 gravitational lensing: weak;
 methods: numerical;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 20 pages, 21 figures