Modeling Galaxies in Redshift Space at the Field Level

TL;DR

This paper introduces an analytical model based on perturbation theory to accurately predict galaxy distributions in redshift space at the field level, confirming theoretical noise corrections and analyzing velocity residuals.

Contribution

It presents a novel perturbation theory-based forward model for redshift-space galaxy density at the field level, validating theoretical noise predictions and analyzing velocity residuals.

Findings

Residual noise is white on large scales, comparable to shot noise.

A $k^2c2$ correction to noise power spectrum is confirmed.

Approximately 10% of galaxies account for half of the velocity residuals.

Abstract

We develop an analytical forward model based on perturbation theory to predict the redshift-space galaxy overdensity at the field level given a realization of the initial conditions. We find that the residual noise between the model and simulated galaxy density has a power spectrum that is white on large scales, with size comparable to the shot noise. In the mildly nonlinear regime, we see a $k^2\mu^2$ correction to the noise power spectrum, corresponding to larger noise along the line of sight and on smaller scales. The parametric form of this correction has been predicted on theoretical grounds before, and our simulations provide important confirmation of its presence. We have also modeled the galaxy velocity at the field-level and compared it against simulated galaxy velocities, finding that about $10\%$ of the galaxies are responsible for half of the rms velocity residual for our simulated galaxy sample.