Redshift drift in a universe with structure II: Light rays propagated through a Newtonian N-body simulation

Abstract

The redshift drift is computed along light rays propagating through a simulated universe based on the Newtonian N-body simulation code GADGET-2 combined with a perturbed Friedmann-Lemaitre-Robertson-Walker metric in the Newtonian gauge. It is found that the mean redshift drift is equal to the drift of the mean redshift to the precision of the numerical computations and that this is due to a high degree of cancellation between two dominant components of the redshift drift. This result is contrary to earlier findings based on inhomogeneous cosmological models exhibiting cosmic backreaction. \newline\indent For simplicity, the results neglect contributions from optical drift. Based on a study of the redshift drift in a Lemaitre-Tolman-Bondi model, the optical drift effects are estimated to be at most of order 10\% of the redshift drift signal. In addition, it is found that the redshift drift contribution from peculiar acceleration of the emitter is negligible in the simulation setup. However, it is expected that the contribution from peculiar acceleration of the emitter is suppressed in the setup due to low resolution of structures and it is hence expected that this contribution will be larger for real observations.