Cosmic-Ray Tracks in Astrophysical Ices: Modeling with the Geant4-DNA Monte Carlo Toolkit

Christopher Shingledecker , Sébastien Incerti (1) , Alexei Ivlev , Dimitris Emfietzoglou , Ioanna Kyriakou , Anton Vasyunin , Paola Caselli

1 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan

Cosmic rays are ubiquitous in interstellar environments, and their bombardment of dust-grain ice mantles is a possible driver for the formation of complex, even prebiotic molecules. Yet, critical data that are essential for accurate modeling of this phenomenon, such as the average radii of cosmic-ray tracks in amorphous solid water (ASW) remain unconstrained. It is shown that cosmic ray tracks in ASW can be approximated as a cylindrical volume with an average radius that is mostly independent of the initial particle energy. Interactions between energetic ions and both a low-density amorphous (LDA) and high-density amorphous (HDA) ice target are simulated using the Geant4-DNA Monte Carlo toolkit, which allows for tracking secondary electrons down to subexcitation energies in the material. We find the peak track core radii, r cyl , for LDA and HDA ices to be 9.9 nm and 8.4 nm, respectively-somewhat less than double the value of 5 nm often assumed in astrochemical models.

Domaines: Astrophysique [astro-ph]; Physique Générale [physics.gen-ph]; Informatique [cs]

Christopher Shingledecker, Sébastien Incerti, Alexei Ivlev, Dimitris Emfietzoglou, Ioanna Kyriakou, et al.. Cosmic-Ray Tracks in Astrophysical Ices: Modeling with the Geant4-DNA Monte Carlo Toolkit. The Astrophysical Journal, 2020, 904 (2), pp.189. ⟨10.3847/1538-4357/abbb30⟩. ⟨hal-03039403⟩