NBIA Seminar: Sarah Recchia

Galactic cosmic rays (GCRs) are thought to be accelerated in strong shocks induced by massive star winds and supernova explosions sweeping across the interstellar medium. However, the phase of the interstellar medium from which the CRs are extracted has remained elusive until now. We investigate the GCR source composition deduced from recent measurements by the AMS-02, Voyager 1, and SuperTIGER experiments to obtain information on the composition, ionization state, and dust content of the GCR source reservoirs. We show that the volatile elements are mainly accelerated from a hot medium typical of Galactic superbubbles. The overabundance of 22Ne most likely arises from acceleration of massive star winds in their termination shocks. The GCR source composition also shows evidence for a preferential acceleration of refractory elements contained in interstellar dust. We suggest that the GCR refractories are also produced in superbubbles.