Density and temperature of cosmic-web filaments on scales of tens of megaparsecs

TL;DR

This study measures the physical properties of large-scale cosmic web filaments using Planck data, detecting the Sunyaev-Zel'dovich effect and gravitational lensing, and estimates their density, temperature, and baryon content.

Contribution

First detection of the thermal Sunyaev-Zel'dovich signal in large-scale filaments on tens of megaparsecs, providing new insights into cosmic web matter properties.

Findings

Detected SZ signal at 4.4 sigma significance

Detected CMB lensing at 8.1 sigma significance

Estimated filament gas temperature around 1.2 million K

Abstract

We studied physical properties of matter in 24,544 filaments ranging from 30 to 100 Mpc in length, identified in the Sloan Digital Sky Survey (SDSS). We stacked the Comptonization y map produced by the Planck Collaboration around the filaments, excluding the resolved galaxy groups and clusters above a mass of ~3*10^13 Msun. We detected the thermal Sunyaev-Zel'dovich signal for the first time at a significance of 4.4 sigma in filamentary structures on such a large scale. We also stacked the Planck cosmic microwave background (CMB) lensing convergence map in the same manner and detected the lensing signal at a significance of 8.1 sigma. To estimate physical properties of the matter, we considered an isothermal cylindrical filament model with a density distribution following a beta-model (beta=2/3). Assuming that the gas distribution follows the dark matter distribution, we estimate that the central gas and matter overdensity and gas temperature are overdensity = (19.0 +27.3 -12.1) and temperature = (1.2 +- 0.4)*10^6 K, which results in a measured baryon fraction of (0.080 +0.116 -0.051) * Omega_b.