A Revised Description of the Cosmic Ray-Induced Desorption of Interstellar Ices

Abstract

Non-thermal desorption of ices on interstellar grains is required to explain observations of molecules that are not synthesized efficiently in the gas phase in cold dense clouds. Perhaps the most important non-thermal desorption mechanism is one induced by cosmic rays (CRs), which, when passing through a grain, heat it transiently to a high temperature - the grain cools back to its original equilibrium temperature via the (partial) sublimation of the ice. Current cosmic-ray-induced desorption (CRD) models assume a fixed grain cooling time. In this work we present a revised description of CRD in which the desorption efficiency depends dynamically on the ice content. We apply the revised desorption scheme to two-phase and three-phase chemical models in physical conditions corresponding to starless and prestellar cores, and to molecular cloud envelopes. We find that inside starless and prestellar cores, introducing dynamic CRD can decrease gas-phase abundances by up to an order of magnitude in two-phase chemical models. In three-phase chemical models our model produces very similar results to the static cooling scheme - when only one monolayer of ice is considered active. Ice abundances are generally insensitive to variations in the grain cooling time. Further improved CRD models need to take into account additional effects in the transient heating of the grains, introduced for example by the adoption of a spectrum of CR energies.

Accepted to ApJ; note significant changes to the model results compared to the version of the paper previously posted on arXiv, especially for low volume densities and for the three-phase ice models, induced by the addition of an upper limit to the CRD rate

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Cited by in corpus (14)

• The complex organic molecular content in the L1517B starless core
• Modelling Deuterated Isotopologues of Methanol toward the Pre-Stellar Core L1544
• H2CS deuteration maps towards the pre-stellar core L1544
• The KOSMA-$\tau$ PDR Model -- I. Recent updates to the numerical model of photo-dissociated regions
• A 3D physico-chemical model of a pre-stellar core. I. Environmental and structural impact on the distribution of CH${}_3$OH and $c$-C${}_3$H${}_2$
• Chemistry and dynamics of the prestellar core L1544
• Astrochemical modelling of infrared dark clouds
• The Effects of Cosmic Rays on the Chemistry of Dense Cores
• Towards a better understanding of ice mantle desorption by cosmic rays
• Oscillations in Gas-grain Astrochemical Kinetics
• The Cosmic-Ray Induced Sputtering Process On Icy Grains
• Impact of ice growth on the physical and chemical properties of dense cloud cores
• Fine-tuning the complex organic molecule formation: sulfur and CO ice as regulators of surface chemistry
• Post-Outburst Chemistry in a Very Low-Luminosity Object: Peculiar High Abundance of Nitric Oxide