Kinematic Sunyaev-Zeldovich Cosmic Microwave Background Temperature Anisotropies Generated by Gas in Cosmic Structures

TL;DR

This paper investigates how gas in cosmic filaments and halos contributes to CMB temperature anisotropies via the Kinematic Sunyaev-Zeldovich effect, potentially explaining observed cold spots and affecting CMB measurements.

Contribution

It provides a detailed computation of the KSZ signal from cosmic filaments and assesses its impact on CMB anisotropies, highlighting its potential significance in cosmological observations.

Findings

KSZ signal from filaments is highly non-Gaussian.

Filaments could explain cold spots in the Corona Borealis Supercluster.

Gas in filaments may contribute notably to CMB anisotropies, improving WMAP data fit.

Abstract

If the gas in filaments and halos shares the same velocity field than the luminous matter, it will generate measurable temperature anisotropies due to the Kinematic Sunyaev-Zeldovich effect. We compute the distribution function of the KSZ signal produced by a typical filament and show it is highly non-gaussian. The combined contribution of the Thermal and Kinematic SZ effects of a filament of size $L\simeq 5$Mpc and electron density $n_e\simeq 10^3m^{-3}$ could explain the cold spots of $\delta\sim -200\mu$K on scales of 30' found in the Corona Borealis Supercluster by the VSA experiment. PLANCK, with its large resolution and frequency coverage, could provide the first evidence of the existence of filaments in this region. The KSZ contribution of the network of filaments and halo structures to the radiation power spectrum peaks around $l\sim 400$, a scale very different from that of clusters of galaxies, with a maximum amplitude $l(l+1)C_l/2\pi\sim 10-25 (\mu K)^2$, depending on model parameters, i.e., $\sigma_8$ and the Jeans length. About 80% of the signal comes from filaments with redshift $z\le 0.1$. Adding this component to the intrinsic Cosmic Microwave Background temperature anisotropies of the concordance model improves the fit to WMAP 3yr data by $\Delta\chi^2\simeq 1$. The improvement is not statistically significant but a more systematic study could demonstrate that gas could significantly contribute to the anisotropies measured by WMAP.