Observing relativistic features in large-scale structure surveys – II. Doppler magnification in an ensemble of relativistic simulations

Abstract

The standard cosmological model is inherently relativistic, and yet a wide range of cosmological observations can be predicted accurately from essentially Newtonian theory. This is not the case on ‘ultra-large’ distance scales, around the cosmic horizon size, however, where relativistic effects can no longer be neglected. In this paper, we present a novel suite of 53 fully relativistic simulations generated using the gevolution code, each covering the full sky out to z ≈ 0.85, and approximately 1930 square degrees out to z ≈ 3.55. These include a relativistic treatment of massive neutrinos, as well as the gravitational potential that can be used to exactly calculate observables on the past light cone. The simulations are divided into two sets, the first being a set of 39 simulations of the same fiducial cosmology (based on the Euclid Flagship 2 cosmology) with different realisations of the initial conditions, and the second which fixes the initial conditions, but varies each of seven cosmological parameters in turn. Taken together, these simulations allow us to perform statistical studies and calculate derivatives of any relativistic observable with respect to cosmological parameters. As an example application, we compute the cross-correlation between the Doppler magnification term in the convergence, κv, and the CDM+baryon density contrast, δcb, which arises only in a (special) relativistic treatment. We are able to accurately recover this term as predicted by relativistic perturbation theory, and study its sample variance and derivatives with respect to cosmological parameters.

Large-scale dark matter simulations

“…Cai et al 2017, or the clustering of galaxies on the past lightcone, e.g. Breton et al 2019;Guandalin et al 2021;Lepori et al 2021;Coates et al 2021, all of which have been proposed as tests of gravitational physics on large scales).…”

The RayGalGroupSims cosmological simulation suite for the study of relativistic effects: An application to lensing-matter clustering statistics

“…Adamek et al (2016b) developed a numerical GR N-body code in the weak-field limit without AMR. Adamek et al (2019) and Lepori et al (2020) implemented a ray-tracing algorithm similar to that of Reverdy (2014) and Breton et al (2019), which solves the geodesic equations without relying on the Born approximation; it was used to investigate several relativistic effects on the weak-lensing convergence power spectrum (Lepori et al 2020), the matter power spectrum multipoles (Guandalin et al 2021), and the cross-correlation power spectrum between the matter-density and lensing convergence (Coates et al 2021).…”

Perspectivas para a física de ultralargas escalas: inflação e efeitos relativísticos

“…cdm = 0.12038, T RCF = 2.7255 K, A s = 2.215 ⇥ 10 9 , n s = 0.9619, N ur = 3.046, e N ncdm = 0, em uma caixa de lado L = 2400 [Mpc/h] que cobre todo o cone de luz (para ver como esses cones de luz são construídos, veja a Fig. 1 de [47]). Cada partícula de matéria escura na simulação tem massa 2.64…”