Weak lensing in the Horizon-AGN simulation lightcone

Abstract

Context. Accurate model predictions including the physics of baryons are required to make the most of the upcoming large cosmological surveys devoted to gravitational lensing. The advent of hydrodynamical cosmological simulations enables such predictions on sufficiently sizeable volumes. Aims. Lensing quantities (deflection, shear, convergence) and their statistics (convergence power spectrum, shear correlation functions, galaxy-galaxy lensing) are computed in the past lightcone built in the Horizon-AGN hydrodynamical cosmological simulation, which implements our best knowledge on baryonic physics at the galaxy scale in order to mimic galaxy populations over cosmic time.Methods. Lensing quantities are generated over a one square degree field of view by performing multiple-lens plane ray-tracing through the lightcone, taking full advantage of the 1 kpc resolution and splitting the line of sight over 500 planes all the way to redshift z ∼ 7. Two methods are explored (standard projection of particles with adaptive smoothing, and integration of the acceleration field) to assert a good implementation. The focus is on small scales where baryons matter most. Results. Standard cosmic shear statistics are impacted at the 10% level by the baryonic component for angular scales below a few arcmin. The galaxy-galaxy lensing signal, or galaxy-shear correlation function, is consistent with measurements for the redshift z ∼ 0.5 massive galaxy population. At higher redshift z 1, the impact of magnification bias on this correlation is relevant for separations greater than 1 Mpc. Conclusions. This work is pivotal for all current and upcoming weak lensing surveys and represents a first step towards building a full end-to-end generation of lensed mock images from large cosmological hydrodynamical simulations.

Weak lensing minima and peaks: Cosmological constraints and the impact of baryons

“…The main effect of baryons on the power spectrum is to suppress power at a few × 100, consistent with results from previous work (e.g. Gouin et al 2019). Baryonic effects suppress positive and deep negative minima, while boosting the κ ≈ 0 minima.…”

The accuracy of weak lensing simulations

“…Wambsganss et al 1998;Jain et al 2000;Hamana & Mellier 2001;Hilbert et al 2009;Harnois-Déraps et al 2012;Petkova et al 2014;Petri 2016) or multiple-sphere algorithm (e.g. Fosalba et al 2008;Das & Bode 2008;Becker 2013;Fabbian et al 2018;Gouin et al 2019b), in which the continuous mass distribution is projected onto a set of discrete two-dimensional mass distributions that act as deflectors along the line-of-sight. There are also methods that bypass the line-of-sight discretization and make use of the three-dimensional mass distribution of the N -body simulation outputs (e.g.…”

Real galaxy mergers from galaxy pair catalogues

“…Concentric shells centered on a fiducial observer located at the origin of the simulation box at z = 0, and containing particles (dark matter, stars and black holes) as well as gas cells, have been extracted on the fly at each coarse time step of the simulation. This allows the creation of a lightcone (Pichon et al 2010;Gouin et al 2019) as sketched in Fig. 1 (top).…”