Tracing Cosmological Signature with Doppler Lensing: Insights from Cosmological Simulations

TL;DR

This study compares two relativistic simulation frameworks, GEVOLUTION and SCREENING, for modeling Doppler lensing effects in cosmic structures, providing guidance on their applicability based on scale and precision needs.

Contribution

It offers a detailed comparison of GEVOLUTION and SCREENING simulations for Doppler lensing, highlighting their scale-dependent performance and suitability for different research objectives.

Findings

GEVOLUTION is recommended for high-precision cosmological tests.

SCREENING offers a computationally efficient alternative for large datasets.

Differences between simulations increase in nonlinear regimes, especially in small voids.

Abstract

Doppler lensing, a relativistic effect resulting from the peculiar velocities of galaxies along the line of sight, provides insight into the large-scale structure of the Universe. Relativistic simulations are essential for modeling Doppler lensing because they incorporate gravity and motion in spacetime. We compare two relativistic $N$-body simulation frameworks, $\texttt{GEVOLUTION}$ and $\texttt{SCREENING}$, to calculate Doppler lensing convergence in cosmic voids of different sizes and halos of different masses. Our analysis reveals scale-dependent performance: $\texttt{SCREENING}$ shows larger differences in small voids (radius range: 15--25 Mpc/h) with a mean absolute relative difference of 38.5\%, due to linearized dynamics failing in nonlinear regimes. Medium voids (25--35 Mpc/h) show better agreement (9.5\% mean difference). For large voids (35--45 Mpc/h), $\texttt{SCREENING}$ exhibits intermediate differences (16.9\% mean difference) with central instabilities. Moreover, our Doppler convergence analysis with massive halos ($10^{11.5}$--$10^{14} {~h^{-1}\mathrm{M}_\odot}$) demonstrates excellent consistency (1.6--3.6\% mean difference). These findings provide clear guidance for simulation choice: $\texttt{GEVOLUTION}$ is recommended for precision studies critical to $\Lambda$CDM or modified gravity tests, while $\texttt{SCREENING}$ offers a computationally efficient alternative for relativistic treatments with large catalogs of voids and halos, assisting future astrophysical surveys.