Galaxy-halo alignments in the Horizon-AGN cosmological hydrodynamical simulation

Understand

Intrinsic alignments of galaxies are a significant astrophysical systematic affecting cosmological constraints from weak gravitational lensing.

• Obtaining numerical predictions from hydrodynamical simulations of expected survey volumes is expensive, and a cheaper alternative relies on populating large dark matter-only simulations with accurate models of alignments calibrated on smaller hydrodynamical runs.
• This requires connecting the shapes and orientations of galaxies to those of dark matter haloes and to the large-scale structure.
• In this paper, we characterise galaxy-halo alignments in the Horizon-AGN cosmological hydrodynamical simulation.