Detection of pure warm-hot intergalactic medium emission from a $7.2$ Mpc long filament in the Shapley supercluster using X-ray spectroscopy

Abstract

A significant fraction of the local Universe's baryonic content remains undetected. Cosmological simulations indicate that most of the missing baryons reside in cosmic filaments in the form of warm-hot intergalactic medium (WHIM). The latter shows low surface brightness and soft X-ray emission, making it challenging to detect. Until now, X-ray WHIM emission has been detected only in very few individual filaments, whereas in even fewer filaments, WHIM has been spectroscopically analyzed. In this work, we used four Suzaku pointings to study the WHIM emission of a filament in the Shapley supercluster, connecting the galaxy cluster pairs A3530/32 and A3528-N/S. We additionally employ XMM-Newton observations to robustly account for point sources in the filament and to fully characterize the neighboring clusters and their signal contamination to the filament region. We report the direct imaging and spectroscopic detection of extended thermal WHIM emission from this single filament. Our imaging analysis confirms the existence of $(21\pm 3)\%$ excess X-ray emission throughout the filament compared to the sky background at a $6.1\sigma$ level. We constrain the filament gas temperature, electron density, and baryon overdensity to be $k_{\text{B}}T\approx (0.8-1.1)$ keV, $n_{\text{e}}\approx 10^{-5}$ cm${}^{-3}$, and ${\delta }_{\text{b}}\approx (30-40)$, respectively, at a $>3\sigma$ detection level, in agreement with cosmological simulations for the first time for a single filament. Independent of the X-ray analysis, we also identify a spectroscopic galaxy overdensity throughout the filament using the Shapley Supercluster velocity Database and constrain the filament's 3D length to be 7.2 Mpc. Overall, this is the first X-ray spectroscopic detection of pure WHIM emission from an individual, pristine filament without significant contamination from unresolved point sources and gas clumps.

18 pages, 7 figures, published in A&A, press releases by ESA, NOVA, SRON, Uni Bonn, Uni Paris-Saclay, and others

References in corpus (24)

• A census of baryons in the Universe from localized fast radio bursts
• The Chandra Deep Field-South Survey: 7 Ms Source Catalogs
• Scaling Properties of a Complete X-ray Selected Galaxy Group Sample
• XMM-Newton and Chandra Cross Calibration Using HIFLUGCS Galaxy Clusters: Systematic Temperature Differences and Cosmological Impact
• Probing cosmic isotropy with a new X-ray galaxy cluster sample through the $L_{\text{X}}-T$ scaling relation
• Detection of hot gas in the filament connecting the clusters of galaxies Abell 222 and Abell 223
• X-Ray morphological analysis of the Planck ESZ clusters
• IACHEC Cross-Calibration of Chandra, NuSTAR, Swift, Suzaku, and XMM-Newton with 3C 273 and PKS 2155-304
• The XMM Large Scale Structure survey: The X-ray pipeline and survey selection function
• Gas and galaxies in filament between clusters of galaxies: The study of A399-A401
• The Abell 3391/95 galaxy cluster system: A 15 Mpc intergalactic medium emission filament, a warm gas bridge, infalling matter clumps, and (re-) accelerated plasma discovered by combining SRG/eROSITA data with ASKAP/EMU and DECam data
• First detection of stacked X-ray emission from cosmic web filaments
• An EAGLE view of the missing baryons
• FUV and X-ray absorption in the Warm-Hot Intergalactic Medium
• Finding the missing baryons in the intergalactic medium with localized fast radio bursts
• Discovery of a Supercluster in the eROSITA Final Equatorial Depth Survey: X-ray Properties, Radio Halo, and Double Relics
• Suzaku Observations of the Outskirts of the Galaxy Cluster Abell 3395 including a Filament toward Abell 3391
• Projection effects in galaxy cluster samples: insights from X-ray redshifts
• The SRG/eROSITA diffuse soft X-ray background. I. The local hot bubble in the western Galactic hemisphere
• Warm-hot gas in groups and galaxies toward H2356-309
• A Systematic Comparison of Galaxy Cluster Temperatures Measured with NuSTAR and Chandra
• Searching for the warm-hot intergalactic medium using XMM-Newton high-resolution X-ray spectra
• Cosmic metal invaders: Intergalactic OVII as a tracer of the warm-hot intergalactic medium within cosmic filaments in the EAGLE simulation
• X-ray and optical analysis of the distant, merging double cluster SPT-CLJ2228-5828, its gas bridge, and shock front