A hot gaseous galaxy halo candidate with Mg X absorption

Abstract

The hot gas in galaxy halos may account for a significant fraction of missing baryons in galaxies, and some of these gases can be traced by high ionization absorption systems in QSO UV spectra. Using high S/N ratio $HST$/COS spectra, we discovered a high ionization state system at $z=1.1912$ in the sightline toward \object{LBQS 1435-0134}, and two-components absorption lines are matched for Mg X, Ne VIII, Ne VI, O VI, Ne V, O V, Ne IV, O IV, N IV, O III, and H I. Mg X, detected for the first time ($5.8\sigma$), is a particularly direct tracer of hot galactic halos, as its peak ion fraction occurs near $10^{6.1}\mathrm{K}$, about the temperature of a virialized hot galaxy halo of mass $\sim 0.5M^{\ast }$. With Mg X and NeVIII, a photoionization model cannot reproduce the observed column densities with path lengths of galaxy halos. For collisional ionization models, one or two temperature models do not produce acceptable fits, but a three temperature model or a power law model can produce the observed results. In the power law model, $\mathrm{d}N/\mathrm{d}T=10^{4.4\pm 2.2-[Z/X]}{T}^{1.55\pm 0.41}$ with temperatures in the range $10^{4.39\pm 0.13}\mathrm{K}<T<10^{6.04\pm 0.05}\mathrm{K}$, the total hydrogen column density is $8.2\times 10^{19}(0.3Z_{\odot }/Z)\mathrm{c}{\mathrm{m}}^{-2}$ and the positive power law index indicates most of the mass is at the high temperature end. We suggest that this absorption system is a hot volume-filled galaxy halo rather than interaction layers between the hot halo and cool clouds. The temperature dependence of the column density is likely due to the local mixture of multiple phase gases.

13 pages, 6 figures, 2 tables, accepted to ApJ

References in corpus (16)

• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• The Search for the Missing Baryons at Low Redshift
• A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
• Constraining the Milky Way's Hot Gas Halo with OVII and OVII Emission Lines
• Do Hot Haloes Around Galaxies Contain the Missing Baryons?
• Collisional Ionization Equilibrium for Optically Thin Plasmas. I. Updated Recombination Rate Coefficients for Bare though Sodium-like Ions
• X-Ray Absorption from the Milky Way Halo and the Local Group
• Weighing Galaxy Disks with the Baryonic Tully-Fisher Relation
• A Census of Intrinsic Narrow Absorption Lines in the Spectra of Quasars at z=2-4
• Numerical Study of Turbulent Mixing Layers with Non-Equilibrium Ionization Calculations
• Hot Gaseous Coronae around Spiral Galaxies: Probing the Illustris Simulation
• A STIS Survey for OVI Absorption Systems at 0.12 < z < 0.5 II.: Physical Conditions of the Ionised Gas
• On the Significance of Absorption Features in HST/COS Data
• An HST/COS survey of molecular hydrogen in DLAs & sub-DLAs at z < 1: Molecular fraction and excitation temperature
• HST/COS observations of a new population of associated QSO absorbers
• A compact, metal-rich, kpc-scale outflow in FBQS J0209-0438: Detailed diagnostics from HST/COS extreme UV observations

Cited by in corpus (6)

• The COS Absorption Survey of Baryon Harbors: Unveiling the Physical Conditions of Circumgalactic Gas through Multiphase Bayesian Ionization Modeling
• 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
• {\it HST}/COS Observations of the Warm Ionized Gaseous Halo of NGC 891
• Spatially Resolved Gas Flows Around the Milky Way
• Physical Conditions of Five O VI Absorption Systems Towards PG $1522+101$
• Detection of Low Metallicity Warm Plasma in a Galaxy Overdensity Environment at z ~ 0.2