Evidence of X-ray emission from the Warm Hot Intergalactic Medium

TL;DR

This paper reports the first high-confidence indirect detection of X-ray emission from the Warm Hot Intergalactic Medium using power spectrum analysis of XMM-Newton and eROSITA data, confirming predictions of cosmic web models.

Contribution

It introduces a novel application of power spectrum analysis to detect the Warm Hot Intergalactic Medium's X-ray emission, bridging a critical gap in understanding cosmic filaments.

Findings

Detected X-ray emission consistent with simulations

Separated filament emission from other X-ray sources

Supports the existence of the Warm Hot Intergalactic Medium

Abstract

The Universe has evolved from an initial diffuse, uniform gas to a complex structure that includes both voids and high-density galaxy clusters connected by gaseous filaments, known as the Cosmic Web, and traced by 3D surveys of galaxies. The filamentary structure contains a significant fraction of the baryonic matter and is predicted to be mostly in the form of a moderately high temperature plasma, the Warm Hot Intergalactic Medium. Plasma at this temperature and ionization level emits mostly in soft X-rays. The filamentary structure, however, is hard to detect because the other sources contributing to the Diffuse X-ray Background are much brighter and, currently, there are very few reported detections of emission from the filaments. We report the first high-confidence level indirect detection of X-ray emission from the Warm Hot Intergalactic Medium. Applying the Power Spectrum Analysis to XMM-Newton and eROSITA data, we separated its contribution from other sources modeled in previous studies. Our result is in good agreement with numerical simulations and fills a critical gap in the picture of the large-scale structure of the Universe, in which filamentary gas, galaxies and dark matter interact and co-evolve.