Impact of Redshift Space Distortion on Persistent Homology of cosmic matter density field

TL;DR

This study examines how redshift space distortions affect the topology of cosmic matter density fields using persistent homology, revealing sensitivities of topological features to RSD and the impact of smoothing scales.

Contribution

It introduces an analysis of RSD effects on persistent homology features of cosmic density fields, highlighting the significance of the linear Kaiser effect and persistent entropy as a robust measure.

Findings

RSD causes clusters to shift towards higher thresholds.

Filament loops and voids migrate towards lower thresholds under RSD.

Persistent entropy remains stable against non-linear effects.

Abstract

By employing summary statistics obtained from Persistent Homology (PH), we investigate the influence of Redshift Space Distortions (RSD) on the topology of excursion sets formed through the super-level filtration method applied to three-dimensional matter density fields. The synthetic fields simulated by the Quijote suite in both real and redshift spaces are smoothed by accounting for the Gaussian smoothing function with different scales. The RSD leads a tendency for clusters ($\tilde{\beta}_0$) to shift towards higher thresholds, while filament loops ($\tilde{\beta}_1$) and cosmic voids ($\tilde{\beta}_2$) migrate towards lower thresholds. Notably, $\tilde{\beta}_2$ exhibits greater sensitivity to RSD compared to clusters and independent loops. As the smoothing scales increase, the amplitude of the reduced Betti number curve ($\tilde{\beta}_k$) decreases, and the corresponding peak position shifts towards the mean threshold. Conversely, the amplitude of $\tilde{\beta}_k$ remains almost unchanged with variations in redshift for $z\in[0-3]$. The analysis of persistent entropy and the overall abundance of $k$-holes indicates that the linear Kaiser effect plays a significant role compared to the non-linear effect for $R \gtrsim 30$ Mpc $h^{-1}$ at $z=0$, whereas persistent entropy proves to be a reliable measure against non-linear influences.