Protostars as cosmic-ray factories

Abstract

In recent years a wealth of observations of infrared/millimetre molecular lines in protostars led to estimate an unexpected high value of the cosmic-ray ionisation rate. Radio continuum observations in the same source types detected synchrotron emission that cannot be explained by standard models of cosmic-ray propagation in star-forming regions. We argue that jet shocks as well as shocks on protostellar surfaces can be efficient accelerators of local thermal particles through the first-order Fermi acceleration (or diffusive shock acceleration) mechanism. The presence of cosmic-ray sources within young protostellar objects can have unexpected repercussions on the ionisation degree of protostellar discs, on the process of star and planet formation, and on the chemistry of complex prebiotic molecules.