Influence of galactic arm scale dynamics on the molecular composition of the cold and dense ISM II. Molecular oxygen abundance

Abstract

Molecular oxygen has been the subject of many observational searches as chemical models predicted it to be a reservoir of oxygen. Although it has been detected in two regions of the interstellar medium, its rarity is a challenge for astrochemical models. In this paper, we have combined the physical conditions computed with smoothed particle hydrodynamics (SPH) simulations with our full gas-grain chemical model Nautilus, to study the predicted O2 abundance in interstellar material forming cold cores. We thus follow the chemical evolution of gas and ices in parcels of material from the diffuse interstellar conditions to the cold dense cores. Most of our predicted O2 abundances are below 1e-8 (with respect to the total proton density) and the predicted column densities in simulated cold cores is at maximum a few 1e14 cm-2, in agreement with the non detection limits. This low O2 abundance can be explained by the fact that, in a large fraction of the interstellar material, the atomic oxygen is depleted onto the grain surface (and hydrogenated to form H2O) before O2 can be formed in the gas-phase and protected from UV photo-dissociations. We could achieve this result only because we took into account the full history of the evolution of the physical conditions from the diffuse medium to the cold cores.

Accepted for publication in MNRAS

References in corpus (10)

• SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• The 2014 KIDA network for interstellar chemistry
• Binding energies: new values and impact on the efficiency of chemical desorption
• Molecular oxygen in the rho Ophiuchi cloud
• Detection of interstellar hydrogen peroxide
• The interstellar chemistry of C3H and C3H2 isomers
• Detection of the hydroperoxyl radical HO2 toward ρOph A: Additional constraints on the water chemical network
• Herschel HIFI observations of O${}_2$ toward Orion: special conditions for shock enhanced emission
• A Search for O_2 in CO-depleted Molecular Cloud Cores with Herschel

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• A new analytic approach to infer the cosmic-ray ionization rate in hot molecular cores from HCO${}^{+}$, N${}_2$H${}^{+}$, and CO observations
• Constraints on the non-thermal desorption of methanol in the cold core LDN 429-C
• Influence of galactic arm scale dynamics on the molecular composition of the cold and dense ISM III. Elemental depletion and shortcomings of the current physico-chemical models
• Chemical constraints on the dynamical evolution of the cold core L694
• The Reaction between Atomic Carbon and Molecular Nitrogen as a Source of Cyanamide and Carbodiimide on Interstellar Ices