Revisiting the large-scale CMB anomalies: The impact of the SZ signal from the Local Universe

TL;DR

This study examines how local large-scale structures, especially the Virgo cluster, influence large-scale CMB anomalies through Sunyaev-Zeldovich effects, finding these secondary effects have negligible impact on observed anomalies.

Contribution

It introduces a constrained hydrodynamical simulation of the local Universe to assess the impact of local structures on CMB anomalies, highlighting the limited role of secondary effects.

Findings

Local structures like Virgo significantly affect large-scale CMB features.

Sunyaev-Zeldovich secondary effects have negligible impact on CMB anomalies.

Simulated secondary anisotropies do not explain observed large-scale anomalies.

Abstract

The full sky measurements of the Cosmic Microwave Background (CMB) temperature anisotropies by $\textit{WMAP}$ and $\textit{Planck}$ have highlighted the presence of several unexpected isotropy-breaking features on the largest angular scales. In this work, we investigate the impact of the local large-scale structure on these anomalies through the thermal and kinetic Sunyaev-Zeldovich effects. We use a constrained hydrodynamical simulation that reproduces the local Universe in a box of $500\,h^{-1}\,$Mpc to construct full sky maps of the temperature anisotropies produced by these two CMB secondary effects and discuss their statistical properties on large angular scales. We show the significant role played by the Virgo cluster on these scales, and compare it to theoretical predictions and random patches of the universe obtained from the hydrodynamical simulation $\textit{Magneticum}$. We explore three of the main CMB large-scale anomalies -- i.e., lack of correlation, quadrupole-octopole alignment and hemispherical asymmetry -- , both in the latest $\textit{Planck}$ data (PR4), where they are detected at a similar level to the previous releases, and using the simulated secondaries from the local Universe, verifying their negligible impact.