Massive Warm/Hot Galaxy Coronae. II. Isentropic Model
Open accessAbstract
We construct a new analytic phenomenological model for the extended circumgalactic material (CGM) of L * galaxies. Our model reproduces the O vii /O viii absorption observations of the Milky Way (MW) and the O vi measurements reported by the COS-Halos and eCGM surveys. The warm/hot gas is in hydrostatic equilibrium in an MW gravitational potential, and we adopt a barotropic equation of state, resulting in a temperature variation as a function of radius. A pressure component with an adiabatic index of is included to approximate the effects of a magnetic field and cosmic rays. We introduce a metallicity gradient motivated by the enrichment of the inner CGM by the Galaxy. We then present our fiducial model for the corona, tuned to reproduce the observed O vi –O viii column densities and with a total mass of inside . The gas densities in the CGM are low ( cm −3 ), and its collisional ionization state is modified by the metagalactic radiation field. We show that for O vi -bearing warm/hot gas with typical observed column densities cm −2 at large ( kpc) impact parameters from the central galaxies, the ratio of the cooling to dynamical times, / , has a model-independent upper limit of . In our model, / at large radii is . We present predictions for a wide range of future observations of the warm/hot CGM, from UV/X-ray absorption and emission spectroscopy to dispersion measure and Sunyaev–Zel’dovich cosmic microwave background measurements. We provide the model outputs in machine-readable data files for easy comparison and analysis.
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The circumgalactic medium temperature is close to the virial temperature of the Galaxy, approximately 5 × 10^5 K.
“close to the virial temperature of the Galaxy, T vir ≈ 5 × 10 5 K”
From The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way (2024) · cites this paper as Faerman et al. 2020
Section 2.3 (Boundary Conditions; page unavailable) sets the CGM gas temperature at its outer boundary to the virial temperature, supporting the comparison. But it scales that temperature to about 3.4 × 10^5 K, while the fiducial model in Section 3.1 lists 2.4 × 10^5 K—not the claimed approximately 5 × 10^5 K. The model also allows temperature to vary with radius. (LLM, conf=0.86)
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References 115 · Cited by 71
- Authors
- Faerman, Y., Sternberg, A., & McKee, C. F.
- Affiliations
- Hebrew University of Jerusalem (IL)
- Tel Aviv University (IL)
- University of California, Berkeley (US)
- Corresponding author
- Faerman, Yakov
- Venue
- The Astrophysical Journal
- Publisher
- American Astronomical Society
- Published
- 2020-04-01
- Volume
- 893
- Issue
- 1
- Pages
- 82
- ISSN
- 0004-637X (ISSN-L)
- 1538-4357
- OpenAlex
- W2974179850
- Cited by
- 71
- References
- 115
- Citations by year
- 2026: 6 · 2025: 10 · 2024: 14 · 2023: 12 · 2022: 14 · 2021: 6 · 2020: 9
- FWCI
- 4.57
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- The Astrophysical Journal (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- arXiv (Cornell University)
- Funders
- Amiel Sternberg (DFG/DIP grant STE 1869/2-1 GE625/17-1)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Keywords
- circumgalactic medium, O VI absorption, Milky Way, barotropic equation of state, metallicity gradients, cooling time, Sunyaev-Zel'dovich effect, dispersion measure, magnetic field, L* galaxies
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