The hot circumgalactic medium of the Milky-Way: new insights from XMM-Newton observations

Abstract

We present XMM-Newton observations around the sightline of Mrk 421. The emission spectrum of the Milky Way circumgalactic medium (CGM) shows that a two phase model is a better fit to the data compared to a single phase model; in addition to the warm-hot virial phase at log ($T/$K) = $6.33_{-0.02}^{+0.03}$, a hot super-virial phase at log ($T/$K) = $6.88_{-0.07}^{+0.08}$ is required. Furthermore, we present observations of five fields within 5 degrees of the primary field. Their spectra also require a two-phase model at warm-hot and hot temperatures. The hot phase, first discovered in Das et al. 2019, appears to be widespread. By chemical tagging we show that emission from the supevirial phase comes from the L-shell transitions of Fe XVIII-FeXXII, and that the range of temperatures probed in emission is distinct from that in absorption. We detect scatter in temperature and emission measure (EM) in both the phases, and deduce that there is small-scale density inhomogeneity in the MW CGM. The emitting gas likely has higher density, possibly from regions close to the disk of the MW, while the absorption in the virial phase may arise from low-density gas extended out to the virial radius of the MW. The presence of the super-virial phase far from the regions around the Galactic center implicates physical processes unrelated to the activity at the Galactic center. Hot outflows resulting from star-formation activity throughout the Galactic disk are likely responsible for producing this phase.

18 pages, 10 figures, 4 tables, submitted to the ApJ

References in corpus (24)

• Array Programming with NumPy
• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• The Circumgalactic Medium
• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• Detection of large-scale X-ray bubbles in the Milky Way halo
• A deep X-ray observation of M82 with XMM-Newton
• The Structure of the Local Hot Bubble
• Resolving the Origin of the Diffuse Soft X-ray Background
• Fermi and eRosita bubbles as relics of the past activity of the Galactic black hole
• X-ray and UV spectroscopy of Galactic diffuse hot gas along the LMC X--3 sight line
• A disk-dominated and clumpy circumgalactic medium of the Milky Way seen in X-ray emission
• Simple Yet Powerful: Hot Galactic Outflows Driven by Supernovae
• 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
• Simulating the Fermi Bubbles as Forward Shocks Driven by AGN Jets
• Empirically Constrained Predictions for Metal-Line Emission from the Circumgalactic Medium
• Super-virial temperature or Neon overabundance?: Suzaku observations of the Milky Way circumgalactic Medium
• Probing the structure of the gas in the Milky Way through X-ray high resolution spectroscopy
• Widespread Detection of Two Components in the Hot Circumgalactic Medium of the Milky Way
• Probing the Anisotropy of the Milky Way Gaseous Halo-II: sightline toward Mrk509
• Clues to the origin of Fermi Bubbles from OVIII/OVII line ratio
• Structual Study of Galactic Hot Gas toward Markarian 421 from X-Ray Absorption and Emission Lines
• XMM-Newton Measurement of the Galactic Halo X-ray Emission using a Compact Shadowing Cloud

Cited by in corpus (8)

• The warm-hot circumgalactic medium of the Milky Way as seen by eROSITA
• Quantifying Observational Projection Effects with a Simulation-based hot CGM model
• Understanding the Baryon Cycle: Fueling Star Formation via Inflows in Milky Way-like Galaxies
• On the origin of the $10^7$ K hot emitting gas in the Circumgalactic medium of the Milky Way
• A Sub-solar Fe/O, logT~7.5 Gas Component Permeating the Milky Way's CGM
• Retrieving the hot circumgalactic medium physics from the X-ray radial profile from eROSITA with an IlustrisTNG-based forward model
• Can supernova from runaway stars mimic the signs of absorbing `super-virial' gas?
• Prospects for studying million-degree gas in the Milky Way halo using the forbidden optical [FeX] and [FeXIV] intersystem lines