Theory

Galactic cosmic rays (CRs) are a ubiquitous source of ionization and heating of the interstellar gas. In dense astrophysical environments, such as molecular clouds and pre-stellar cores (where UV and x-ray photons are extinguished), the ionization and heating are completely dominated by CRs. One of the principal aims of the CAS-Theory group is to understand the physics of low-energy CRs in molecular gas, by combining advanced methods of the kinetic theory and plasma physics and applying available observational constraints. more

Using numerical simulations, our group explores the effect of magnetic fields on disk formation, evolution, substructure, and grain growth within the disks. The relative strengths of non-ideal MHD effects determine whether a disk can form at all, as well as the orientation of the disk. Ambipolar diffusion, one important non-ideal MHD effect, removes small grains from the disk, which in turn changes the ambipolar diffusivity and promotes disk formation. The growth of larger grains also depends on the magnetic field: the magneto-rotational instability generates turbulence in the disk, which can result in much faster grain growth compared to the hydrodynamic Kolmogorov turbulence. Finally, the interplay between the magnetic field and the grain growth creates a wealth of substructures in the disks, carving out gaps and rings, where planet formation may occur. more

The astrochemical modelling efforts at CAS aim primarily at understanding chemical evolution in low-mass star-forming regions, in particular in cold and dense cores inside molecular clouds, to understand better the initial conditions of forming protostellar/planetary systems. Particular attention is currently directed to studies of isotope and complex organic molecule chemistry in the gas and in solids, and to the effect of cosmic rays on the chemistry. more

In order to self-consistently study the chemical and physical processes in star formation, we couple the chemistry with hydrodynamic (HD) and magnetohydrodynamic (MHD) models from GMC to protoplanetary disk scales, adopting techniques such as multi-fluid and tracer particles. We aim to provide constraints on the observed chemical differentiations of various species in different star-forming environments.