X-Ray Absorption By WHIM in the Sculptor Wall

TL;DR

This study reports the first simultaneous analysis of XMM and Chandra X-ray data detecting the WHIM in the Sculptor Wall, providing robust evidence for the missing baryons in large-scale cosmic structures.

Contribution

It presents the first robust detection of non-local WHIM via X-ray absorption using simultaneous XMM and Chandra observations with known redshift.

Findings

Detection of O vii K-alpha line at 3-sigma significance

Column density consistent with cosmological simulations

First simultaneous X-ray analysis confirming WHIM presence

Abstract

We present XMM RGS and Chandra LETG observations of the blazar, H 2356-309, located behind the Sculptor Wall, a large-scale galaxy structure expected to harbor high-density Warm-Hot Intergalactic Medium (WHIM). Our simultaneous analysis of the RGS and LETG spectra yields a 3-sigma detection of the crucial redshifted O vii K-alpha line with a column density (>~ 10^{16} cm^{-2}) consistent with similar large-scale structures produced in cosmological simulations. This represents the first detection of non-local WHIM from X-ray absorption studies where XMM and Chandra data are analyzed simultaneously and the absorber redshift is already known, thus providing robust evidence for the expected repository of the "missing baryons".