Constraining the extra heating of the Diffuse Ionized Gas in the Milky Way

Abstract

The detailed observations of the diffuse ionized gas through the emission lines H$\alpha$, [NII], and [SII] in the Perseus Arm of our Galaxy by the Wisconsin H$\alpha$ Mapper (WHAM)--survey challenge photoionization models. They have to explain the observed rise in the line ratios [NII]/H$\alpha$ and [SII]/H$\alpha$. The models described here consider for the first time the detailed observational geometry toward the Perseus Arm. The models address the vertical variation of the line ratios up to height of 2 kpc above the midplane. The rising trends of the line ratios are matched. The increase in the line ratios is reflected in a rise of the temperature of the gas layer. This is due to the progressive hardening of the radiation going through the gas. However an extra heating above photoionization is needed to explain the absolute values. Two different extra heating rates are investigated which are proportional to $n^0$ and $n^1$. The models show that a combination of both are best to explain the data, where the extra heating independent of density is dominant for z $>$ 0.8 kpc.

arXiv commentaccepted for publication in ApJ

References in corpus (14)

• The Wisconsin H-Alpha Mapper Northern Sky Survey
• WHAM Observations of H-Alpha, [S II], and [N II] toward the Orion and Perseus Arms: Probing the Physical Conditions of the Warm Ionized Medium
• Modeling the Warm Ionized Interstellar Medium and Its Impact on Elemental Abundance Studies
• Evidence for an Additional Heat Source in the Warm Ionized Medium of Galaxies
• Escape of Ionizing Radiation from High-Redshift Galaxies
• Where do the disks of spiral galaxies end?
• Ionization Sources and Physical Conditions in the Diffuse Ionized Gas Halos of Four Edge-On Galaxies
• A 3D Monte Carlo Photoionization Code for Modeling Diffuse Ionized Gas
• Monte Carlo Photoionization Simulations of Diffuse Ionized Gas
• Lyman Continuum Escape from Inhomogeneous ISM
• The Warm Ionized Medium in the Milky Way and Other Galaxies
• Extraplanar Emission-Line Gas in Edge-On Spiral Galaxies. II. Optical Spectroscopy
• Searching for additional heating - [OII] emission in the diffuse ionized gas of NGC891, NGC4631 and NGC3079
• Localized magnetic reconnection as a cause of extraplanar diffuse ionised in the halo

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• The warm ionized medium in spiral galaxies
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• 3D Optical Spectroscopic Study of NGC3344 with SITELLE: I. Identification and Confirmation of Supernova Remnants
• Ionized Gas in the First 10 Kiloparsecs of the Interstellar Galactic Halo: Metal Ion Fractions
• Diffuse Ionized Gas inside the dwarf irregular galaxy NGC 6822