Tracing Cosmological Signature with Doppler Lensing: Insights from Cosmological Simulations

TL;DR

The paper investigates Doppler lensing convergence using two relativistic N-body frameworks, Gevolution and Cosmic Screening, across cosmic voids and halos to quantify scale-dependent agreement. Gevolution captures nonlinear relativistic effects for high-precision cosmology, while Screening offers computational efficiency suitable for large catalogs with linearized dynamics. Results show pronounced discrepancies in small voids ( Screening underestimates near flows by ~9.6% and overestimates receding flows by ~15.9%, yielding a mean relative difference around 38.5%), good agreement in medium voids (~9.5%), and moderate errors with instabilities in large voids (~16.9%). Halos show robust consistency (mean $|\Delta_{\rm rel}\kappa|$ ~1.6–3.6%), suggesting Screening is reliable for overdense environments. Overall, the work provides practical guidance for selecting simulation frameworks in upcoming surveys like Euclid and DESI, balancing precision needs against computational efficiency.

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 $Λ$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.

Figures (5)

• Figure 1: Histogram of void radius distributions from 21 realizations of Gevolution (blue) and Screening (orange) simulations, identified using Revolver. The 15--25$~h^{-1}\mathrm{Mpc}$ range shows a 4.2% deficit in Screening voids compared to Gevolution, while larger voids (25--35 and 35--45$~h^{-1}\mathrm{Mpc}$) are nearly equivalent (see Table \ref{['tab:void_optimization']}).
• Figure 2: Doppler lensing convergence for 15--25$~h^{-1}\mathrm{Mpc}$ voids from 21 Gevolution and Screening realizations, showing Screening's biases in nonlinear regimes.
• Figure 3: Doppler lensing convergence for 25--35$~h^{-1}\mathrm{Mpc}$ voids, showing Screening's reliable performance for medium voids.
• Figure 4: Doppler lensing convergence for 35--45$~h^{-1}\mathrm{Mpc}$ voids, indicating Screening's moderate errors due to central instabilities.
• Figure 5: Doppler lensing convergence profiles around massive halos for three representative mass ranges: (a,b) $10^{11.5}$--$10^{12.0}~h^{-1}\mathrm{M}_\odot\xspace$, (c,d) $10^{12.0}$--$10^{12.5}~h^{-1}\mathrm{M}_\odot\xspace$, and (e,f) $10^{12.5}$--$10^{13.0}~h^{-1}\mathrm{M}_\odot\xspace$. Left panels show convergence $\kappa$ and difference $\Delta\kappa$; right panels show relative difference $\Delta_\mathrm{rel}\kappa\xspace$ with $\pm5\%$ region highlighted. The excellent agreement across all these mass ranges contrasts with the significant discrepancies found in small voids.