The Origin of the Hot Gas in the Galactic Halo: Confronting Models with XMM-Newton Observations

Abstract

We compare the predictions of three physical models for the origin of the hot halo gas with the observed halo X-ray emission, derived from 26 high-latitude XMM-Newton observations of the soft X-ray background between $l=120\degr$ and $l=240\degr$. These observations were chosen from a much larger set of observations as they are expected to be the least contaminated by solar wind charge exchange emission. We characterize the halo emission in the XMM-Newton band with a single-temperature plasma model. We find that the observed halo temperature is fairly constant across the sky (~1.8e6-2.3e6 K), whereas the halo emission measure varies by an order of magnitude (~0.0005-0.006 cm^-6 pc). When we compare our observations with the model predictions, we find that most of the hot gas observed with XMM-Newton does not reside in isolated extraplanar supernova remnants -- this model predicts emission an order of magnitude too faint. A model of a supernova-driven interstellar medium, including the flow of hot gas from the disk into the halo in a galactic fountain, gives good agreement with the observed 0.4-2.0 keV surface brightness. This model overpredicts the halo X-ray temperature by a factor of ~2, but there are a several possible explanations for this discrepancy. We therefore conclude that a major (possibly dominant) contributor to the halo X-ray emission observed with XMM-Newton is a fountain of hot gas driven into the halo by disk supernovae. However, we cannot rule out the possibility that the extended hot halo of accreted material predicted by disk galaxy formation models also contributes to the emission.

20 pages, 14 figures. New version accepted for publication in ApJ. Changes include new section discussing systematic errors (Section 3.2), improved method for characterizing our model spectra (4.2.2), changes to discussion of other observations (5.1). Note that we can no longer rule out possibility that extended hot halo of accreted material contributes to observed halo emission (see 5.2.1)

References in corpus (12)

• Turbulent Structure of a Stratified Supernova-Driven Interstellar Medium
• X-ray coronae in simulations of disc galaxy formation
• Where are the ``Missing'' Galactic Baryons?
• OVII and OVIII line emission in the diffuse soft X-ray background: heliospheric and galactic contributions
• Identifying XMM-Newton observations affected by solar wind charge exchange - Part I
• The Origin and Kinematics of Cold Gas in Galactic Winds: Insight from Numerical Simulations
• X-ray and UV spectroscopy of Galactic diffuse hot gas along the LMC X--3 sight line
• Xmm-Newton Observations of the Diffuse X-ray Background
• An XMM-Newton Survey of the Soft X-ray Background. I. The O VII and O VIII Lines Between l=120 and l=240
• Properties of the Diffuse X-ray Background toward MBM20 with Suzaku
• Determining The Galactic Halo's Emission Measure from UV and X-ray Observations
• A Possible Supernova Remnant high above the Galactic Disk

Cited by in corpus (54)

• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• Constraining the Milky Way's Hot Gas Halo with OVII and OVII Emission Lines
• Launching cosmic-ray-driven outflows from the magnetized interstellar medium
• Vertical structure of a supernova-driven turbulent magnetized ISM
• Massive Warm/Hot Galaxy Coronae as Probed by UV/X-ray Oxygen Absorption and Emission: I - Basic Model
• Suzaku observations of the diffuse x-ray emission across the fermi bubbles' edges
• An XMM-Newton Survey of the Soft X-ray Background. III. The Galactic Halo X-ray Emission
• Gas Condensation in the Galactic Halo
• The Rotation of the Hot Gas Around the Milky Way
• The Fates of the Circumgalactic Medium in the FIRE Simulations
• A Census of Baryons and Dark Matter in an Isolated, Milky Way-sized Elliptical Galaxy
• Characterizing Transition Temperature Gas in the Galactic Corona
• Massive Warm/Hot Galaxy Coronae: II. Isentropic Model
• An FRB Sent Me a DM: Constraining the Electron Column of the Milky Way Halo with Fast Radio Burst Dispersion Measures from CHIME/FRB
• Simulations of High-Velocity Clouds. I. Hydrodynamics and High-Velocity High Ions
• The effect of an expanding universe on massive objects
• The Circumgalactic Medium of Milky Way-like Galaxies in the TNG50 Simulation -- I: Halo Gas Properties and the Role of SMBH Feedback
• An XMM-Newton Survey of the Soft X-ray Background. II. An All-Sky Catalog of Diffuse O VII and O VIII Emission Intensities
• Discovery of a very hot phase of the Milky Way CGM with non-solar abundance ratios
• X-ray and Gamma-ray Observations of the Fermi Bubbles and NPS/Loop I Structures
• Abundance and temperature of the outer hot circum-Galactic medium: The SRG/eROSITA view of the soft X-ray background in the eFEDS field
• Frontier Fields Clusters: Chandra and JVLA View of the Pre-Merging Cluster MACS J0416.1-2403
• Multiple temperature components of the hot circumgalactic medium of the Milky Way
• The hot circumgalactic medium of the Milky Way: evidence for super-virial, virial, and sub-virial temperature, non-solar chemical composition, and non-thermal line broadening
• The ELIXR Galaxy Survey. II: Baryons and Dark Matter in an Isolated Elliptical Galaxy
• HaloSat -- A CubeSat to Study the Hot Galactic Halo
• Super-virial temperature or Neon overabundance?: Suzaku observations of the Milky Way circumgalactic Medium
• Probing the anisotropy of the Milky Way gaseous halo: Sight-lines toward Mrk 421 and PKS2155-304
• Effect of the heating rate on the stability of the three-phase interstellar medium
• A Data-Driven Technique Using Millisecond Transients to Measure the Milky Way Halo
• Probing the Anisotropy of the Milky Way Gaseous Halo-II: sightline toward Mrk509
• Evidence for massive warm-hot circumgalactic medium around NGC 3221
• CGM properties in VELA and NIHAO simulations; the OVI ionization mechanism: dependence on redshift, halo mass and radius
• A Young GMC Formed at the Interface of Two Colliding Supershells: Observations Meet Simulations
• The onset of large scale turbulence in the interstellar medium of spiral galaxies
• XMM-Newton and Suzaku X-ray Shadowing Measurements of the Solar Wind Charge Exchange, Local Bubble, and Galactic Halo Emission
• Suzaku X-ray Observations of the Fermi Bubbles: Northernmost Cap and Southeast Claw Discovered with MAXI-SSC
• Detection of thermal Sunyaev-Zel'dovich Effect in the circumgalactic medium of low-mass galaxies -- a surprising pattern in self-similarity and baryon sufficiency
• The hot circumgalactic medium of the Milky-Way: new insights from XMM-Newton observations
• Empirical estimates of the Galactic halo contribution to the dispersion measures of extragalactic fast radio bursts using X-ray absorption
• The Origin of the Hot Gas in the Galactic Halo: Testing Galactic Fountain Models' X-ray Emission
• The X-ray emission in young radio AGNs
• Origin of Galactic Spurs: New Insight from Radio/X-ray All-sky Maps
• Introducing the Condor Array Telescope: IV. A possible nova super-remnant surrounding the putative recurrent nova KT Eridani
• High-ion absorption in the proximate damped Lyman-alpha system toward Q0841+129
• On the patchy appearance of the circum-Galactic medium and the influence of foreground absorption
• eROSITA narrowband maps at the energies of soft X-ray emission lines
• The Diffuse Ionized Gas of the Large Magellanic Cloud
• XMM-Newton Measurement of the Galactic Halo X-ray Emission using a Compact Shadowing Cloud
• Is the Milky Way's Hot Halo Convectively Unstable?
• A Sub-solar Fe/O, logT~7.5 Gas Component Permeating the Milky Way's CGM
• The collisions of high-velocity clouds with the galactic halo
• Clumpy shocks as the driver of velocity dispersion in molecular clouds: the effects of self-gravity and magnetic fields
• Constraints on cosmic rays in the Milky Way circumgalactic medium from OVIII observations