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 ensure a good implementation. The focus is on small scales where baryons matter most. Results. Standard cosmic shear statistics are affected at the 10% level by the baryonic component for angular scales below a few arcminutes. 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 effect 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.
Highlights
Gravitational lensing has become a versatile tool for probing the cosmological model and scenarios of galaxy evolution
Lensing quantities and their statistics are computed in the past lightcone built in the Horizon-active galactic nuclei (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
From the coherent distortions, generated by the intervening matter along the line of sight, of the last scattering surface (e.g. Planck Collaboration VIII 2018) or intermediate-redshift galaxies (Bartelmann & Schneider 2001; Kilbinger 2015), to the inner parts of massive galaxies (Treu 2010), lensing directly measures the fractional energy density in matter of the Universe. Because it does not rely on assumptions about the relative distribution between the galaxies and the underlying dark matter (DM), which drives the dynamical evolution of cosmological structures, weak lensing plays a key role in recent, ongoing, or upcoming ground-based imaging surveys, such as the Canada France Hawaii Lensing Survey (Heymans et al 2012), the Dark Energy Survey (Dark Energy Survey Collaboration 2005; Abbott et al 2016), the Kilo-Degree Survey (KiDS: Kuijken et al 2015), the Hyper Suprime-Cam Subaru Strategic Survey (Miyazaki et al 2012), and the Large Synoptic Survey Telescope (LSST Science Collaborations 2009)
Summary
Gravitational lensing has become a versatile tool for probing the cosmological model and scenarios of galaxy evolution. By taking advantage of the lightcone that is generated during the simulation run, we are able to fully account for projection effects (mixing physical scales) and small-scale non-linearities occurring in the propagation of light rays (e.g., Born approximation, lens-lens coupling, corrections for shear – reduced shear) that may be boosted by the steepening of the gravitational potential wells that are caused by cooled gas that sinks to the bottom of DM halos This extends the analysis of Chisari et al (2018), who mostly focused on the effect of baryons on the three-dimensional matter power spectrum and compared the Horizon-AGN results with those of Illustris, OWLS, EAGLE, and Illustris-TNG and found a broad qualitative agreement.
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