Evidence for the Missing Baryons in the Angular Correlation of the Diffuse X-ray Background

TL;DR

This study provides evidence that a significant portion of the universe's missing baryons resides in the Warm-Hot Intergalactic Medium, detected through their influence on the diffuse X-ray background's angular correlation.

Contribution

It presents the first detection of the missing baryons in the WHIM via angular correlation analysis of diffuse X-ray emission using XMM-Newton data.

Findings

12% of diffuse X-ray emission is from intergalactic filaments

Detection significance exceeds several sigmas

Results support the presence of the missing baryons in the WHIM

Abstract

The amount of detected baryons in the local Universe is at least a factor of two smaller than measured at high redshift. It is believed that a significant fraction of the baryons in the current Universe is "hiding" in a hot filamentary structure filling the intergalactic space, the Warm-Hot Intergalactic Medium ($WHIM$). We found evidence of the missing baryons in the $WHIM$ by detecting their signature on the angular correlation of diffuse X-ray emission with the XMM-Newton satellite. Our result indicates that $(12\pm 5)$% of the total diffuse X-ray emission in the energy range 0.4-0.6 keV is due to intergalactic filaments. The statistical significance of our detection is several sigmas ($\chi ^2>136$ N=19). The error bar in the X-ray flux is dominated, instead, by cosmic variation and model uncertainties.