CO+ in M 82: A Consequence of Irradiation by X-rays

Abstract

Based on its strong CO+ emission it is argued that the M 82 star-burst galaxy is exposed to a combination of FUV and X-ray radiation. The latter is likely to be the result of the star-burst superwind, which leads to diffuse thermal emission at ~0.7 keV, and a compact hard, 2-10 keV, source (but not an AGN). Although a photon-dominated region (FUV) component is clearly present in the nucleus of M 82, and capable of forming CO+, only X-ray irradiated gas of density 10^3-10^5 cm^-3 can reproduce the large, ~(1-4)x10^13 cm^-2, columns of CO+ that are observed toward the proto-typical star-burst M 82. The total X-ray luminosity produced by M 82 is weak, ~10^41 erg s^-1, but this is sufficient to drive the formation of CO+.

added discussion on more recent X-ray observations

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• The Orbital Period of the Ultraluminous X-ray Source in M82
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Cited by in corpus (19)

• Dense gas in luminous infrared galaxies
• Lambda = 3 mm line survey of nearby active galaxies
• A lambda = 1.3 mm and 2 mm molecular line survey towards M82
• Warm Molecular Hydrogen in the Galactic Wind of M82
• Photodissociation chemistry footprints in the Starburst galaxy NGC 253
• On the chemistry and distribution of HOC+ in M82: More evidence for extensive PDRs
• Detection of extragalactic H3O+
• 3 mm spectral line survey of two lines of sight toward two typical cloud complexes in the Galactic Center
• Probing X-ray irradiation in the nucleus of NGC 1068 with observations of high-J lines of dense gas tracers
• Starburst Energy Feedback Seen Through HCO${}^{+}$/HOC${}^{+}$ Emission in NGC 253 from ALCHEMI
• A New Radio Molecular Line Survey of Planetary Nebulae: HNC/HCN as a Diagnostic of Ultraviolet Irradiation
• Excitation and abundance study of CO+ in the interstellar medium
• The first CO+ image: Probing the HI/H2 layer around the ultracompact HII region Mon R2
• Excitation of the molecular gas in the nuclear region of M82
• Mapping NGC 7027 in New Light: CO${}^{+}$ and HCO${}^{+}$ Emission Reveal Its Photon- and X-ray-Dominated Regions
• The chemical footprint of the star formation feedback in M 82 on scales of 100 pc
• On the effects of UV photons/X-rays on the chemistry of the Sgr B2 cloud
• Extragalactic H3O+: Some Consequences
• Infrared view of the multiphase ISM in NGC 253 II. Modelling the ionised and neutral atomic gas