Tracing the 10${}^7$K Warm-Hot Intergalactic Medium with UV absorption lines

Abstract

Today, the majority of the cosmic baryons in the Universe are not observed directly, leading to an issue of "missing baryons" at low redshift. Cosmological hydrodynamical simulations have indicated that a significant portion of them will be converted into the so-called Warm-Hot Intergalactic Medium (WHIM), with gas temperature ranging between 10${}^5$-10${}^7$K. While the cooler phase of this gas has been observed using O VI and Ne VIII absorbers at UV wavelengths, the hotter fraction detection relies mostly on observations of O VII and O VIII at X-ray wavelengths. Here, we target the forbidden line of [Fe XXI] $\lambda$ 1354$\unicode{x212B}$ which traces 10${}^7$K gas at UV wavelengths, using more than one hundred high-spectral resolution (R$\sim$49,000) and high signal to noise VLT/UVES quasar spectra, corresponding to over 600 hrs of VLT time observations. A stack of these at the position of known DLAs lead to a 5-$\sigma$ limit of $\log [\mathrm{N}([\mathrm{Fe}\mathrm{XXI}])]<$17.4 ($E{W}_{rest}<22$m$\unicode{x212B}$), three orders of magnitude higher than the expected column density of the WHIM $\log [\mathrm{N}([\mathrm{Fe}\mathrm{XXI}])]<$14.5. This work proposes an alternative to X-ray detected 10${}^7$K WHIM tracers, by targeting faint lines at UV wavelengths from the ground benefiting from higher instrumental throughput, enhanced spectral resolution, longer exposure times and increased number of targets. The number of quasar spectra required to reach this theoretical column density with future facilities including 4MOST, ELT/HIRES, MSE and the Spectroscopic Telescope appears challenging at present. Probing the missing baryons is essential to constrain the accretion and feedback processes which are fundamental to galaxy formation.

Accepted for publication MNRAS

References in corpus (31)

• The Circumgalactic Medium
• A census of baryons in the Universe from localized fast radio bursts
• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• The Search for the Missing Baryons at Low Redshift
• Metallicity Evolution of Damped Lyman-alpha Systems out to z~5
• The Cosmic Baryon and Metal Cycles
• 4MOST: Project overview and information for the First Call for Proposals
• The COS-Halos Survey: Metallicities in the Low-Redshift Circumgalactic Medium
• A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
• Cosmic dynamics in the era of Extremely Large Telescopes
• The Low-z Intergalactic Medium. III. HI and Metal Absorbers at z<0.4
• The Half Million Quasars (HMQ) Catalogue
• Physical Properties, Baryon Content, and Evolution of the LyαForest: New Insights from High Resolution Observations at z < 0.4
• The Properties of Low Redshift Intergalactic O VI Absorbers Determined from High S/N Observations of 14 QSOs with the Cosmic Origins Spectrograph
• Multi-phase Circum-Galactic Medium probed with MUSE and ALMA
• Detection of the Missing Baryons toward the Sightline of H1821+643
• MUSE-ALMA Halos V: Physical properties and environment of z < 1.4 HI quasar absorbers
• On the Significance of Absorption Features in HST/COS Data
• The Physical Origins of the Identified and Still Missing Components of the Warm-Hot Intergalactic Medium: Insights from Deep Surveys in the Field of Blazar 1ES1553+113
• Numerical simulations of the Warm-Hot Intergalactic Medium
• Detection of missing baryons in galaxy groups with kinetic Sunyaev-Zel'dovich effect
• The Detailed Science Case for the Maunakea Spectroscopic Explorer, 2019 edition
• WEAVE-QSO: A Massive Intergalactic Medium Survey for the William Herschel Telescope
• Finding the Missing Baryons Using CMB as a Backlight
• 4MOST Consortium Survey 6: Active Galactic Nuclei
• Investigating lensing by absorbers in the 2dF-Quasar survey
• Metal-enriched Galaxies in the First ~1 Billion Years: Evidence of a Smooth Metallicity Evolution at z ~ 5
• The Future of Multi-Object Spectroscopy: a ESO Working Group Report
• Comments on "A huge reservoir of ionized gas around the Milky Way: accounting for the missing mass?" (2012 ApJL, 756, 8) and "The warm-hot gaseous halo of the Milky Way" (arXiv1211.3137)
• The OVI mystery: mismatch between X-ray and UV column densities
• Strong z~0.5 O VI Absorption Toward PKS 0405-123: Implications for Ionization and Metallicity of the Cosmic Web

Cited by in corpus (3)

• 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
• Cosmic metal density evolution in neutral gas: insights from observations and cosmological simulations
• Searching for cold gas traced by MgII quasar absorbers in massive X-ray-selected galaxy clusters