Astrophys. J., 893, 82-82 (2020/April-2)
Massive warm/hot galaxy coronae. II. Isentropic model.
FAERMAN Y., STERNBERG A. and McKEE C.F.
Abstract (from CDS):
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 γ=4/3 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 MCGM~5.5×1010M☉ inside rCGM~280kpc. The gas densities in the CGM are low (nH=10–5–3×10–4 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 NOVI∼3×1014 cm–2 at large (≳100 kpc) impact parameters from the central galaxies, the ratio of the cooling to dynamical times, tcool/tdyn, has a model-independent upper limit of ≲4. In our model, tcool/tdyn at large radii is ∼2–3. 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.
© 2020. The American Astronomical Society. All rights reserved.
Circumgalactic medium - Galaxy structure - Galaxy dark matter halos - Quasar absorption line spectroscopy - Interstellar medium - Galaxy formation - Milky Way formation - Intergalactic medium - Galactic and extragalactic astronomy
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