Electron Distribution in the Galactic Disk - Results From a Non-Equilibrium Ionization Model of the ISM

Abstract

Using three-dimensional non-equilibrium ionization (NEI) hydrodynamical simulation of the interstellar medium (ISM), we study the electron density, $n_e$, in the Galactic disk and compare it with the values derived from dispersion measures towards pulsars with known distances located up to 200 pc on either side of the Galactic midplane. The simulation results, consistent with observations, can be summarized as follows: (i) the DMs in the simulated disk lie between the maximum and minimum observed values, (ii) the log <n_e> derived from lines of sight crossing the simulated disk follows a Gaussian distribution centered at μ=-1.4 with a dispersion σ=0.21, thus, the Galactic midplane <n_e>=0.04\pm 0.01$cm$^{-3}$, (iii) the highest electron concentration by mass (up to 80%) is in the thermally unstable regime (200<T<10^{3.9} K), (iv) the volume occupation fraction of the warm ionized medium is 4.9-6%, and (v) the electrons have a clumpy distribution along the lines of sight.

Letter accepted for publication in Monthly Notices of the Royal Astronomical Society

References in corpus (9)

• The chemical composition of the Sun
• The Vertical Structure of Warm Ionised Gas in the Milky Way
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• Density probability distribution functions of diffuse gas in the Milky Way
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• An Ultra-long Wavelength Sky Model with Absorption Effect
• Photoionisation and Heating of a Supernova Driven, Turbulent, Interstellar Medium
• Topological signatures of interstellar magnetic fields - I. Betti numbers and persistence diagrams
• Halpha and [S II] emission from warm ionized gas in the Scutum-Centaurus Arm
• Radiation hydrodynamics simulations of the evolution of the diffuse ionized gas in disc galaxies