Discovery of a multiphase OVI and OVII absorber in the circumgalactic/intergalactic transition region

Abstract

The observational constraints on the baryon content of the WHIM rely almost entirely on FUV measurements. However, cosmological, hydrodynamical simulations predict strong correlations between the spatial distributions of FUV and X-ray absorbing WHIM. In this work we investigate this prediction by analyzing XMM-Newton X-ray counterparts of FUV-detected intergalactic OVI absorbers known from FUSE and HST/STIS data, and compare this information to the predictions of simulations. We study the X-ray absorption at the redshift of the only significantly detected OVI absorber in the TonS180 sightline's FUV spectrum, found at $z=0.04579\pm 0.00001$. We characterize the spectral properties of the OVI-OVIII absorbers and explore the ionization processes behind the measured absorption. The observational results are compared to the predicted warm-hot gas properties in the EAGLE simulation to infer the physical conditions of the absorber. We detect both OVI and OVII absorption at a $5\sigma$ confidence level, whereas OVIII absorption is not detected. CIE modeling constrains the X-ray absorbing gas temperature to log$T_{CIE}$(K)$=6.22\pm 0.05$ with a total hydrogen column density $N_H=5.8_{-2.2}^{+3.0}\times Z_{sun}/Z_{abs}\times 10^{19}$ cm${}^{-2}$. This model predicts an OVI column density consistent with that measured in the FUV, but our limits on the OVI line width indicate >90 % likelihood that the FUV-detected OVI arises from a different, cooler phase. We find that the observed absorber lies about a factor of two further away from the detected galaxies than is the case for similar systems in EAGLE. Understanding the abundance of the systems similar to the one considered in this work helps to define the landscape for WHIM searches with future X-ray telescopes.

Accepted for publication in A\&A

References in corpus (12)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
• A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
• The Low-z Intergalactic Medium. III. HI and Metal Absorbers at z<0.4
• CalFUSE v3: A Data-Reduction Pipeline for the Far Ultraviolet Spectroscopic Explorer
• Detection of the Missing Baryons toward the Sightline of H1821+643
• Equilibration processes in the Warm-Hot Intergalactic Medium
• The abundance and physical properties of O VII and O VIII X-ray absorption systems in the EAGLE simulations
• 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
• HST/COS observations of a new population of associated QSO absorbers
• HST/COS detection of a Ne VIII absorber towards PG 1407+265: An unambiguous tracer of collisionally ionized hot gas?
• Hot WHIM counterparts of FUV OVI absorbers: Evidence in the line-of-sight towards quasar 3C 273

Cited by in corpus (5)

• Soft X-ray emission from warm gas in IllustrisTNG circum-cluster environments
• Systematic errors in the maximum likelihood regression of Poisson count data: introducing the overdispersed chi-square distribution
• Galaxy cluster photons alter the ionisation state of the nearby warm-hot intergalactic medium
• The Three Hundred: Gas Properties Outside of Galaxy Cluster with the WHIM Contribution and Detection
• Prospects for detecting the circum- and intergalactic medium in X-ray absorption using the extended intracluster medium as a backlight