Cosmic rays: A view into galactic interactions and the new physics

Abstract

It is known that close galactic fly-bys and interactions give rise to shock waves that disrupt the interstellarmediumof galaxies and impact their morphologies. These large-scale shocks that form in the interstellar medium of interacting systems will be the sites of particle acceleration giving rise to a population of tidal cosmic rays, in addition to standard galactic cosmic rays present in star-forming galaxies. Abundance measurements in such systems can help us probe the presence of this cosmic-ray population and in turn test the long-lasting primordial lithium problem and the need for the new physics. Such additional cosmic-ray population will also result in non-thermal radiation which will affect the radio brightness of these galaxies and in turn impact the wellestablished far infrared-radio correlation, standardly used as a star-formation rate tracer, among other things. Finally, we will discuss how radio and infrared signatures of these cosmic rays can in turn be used as indicators of galactic interactions which could be especially powerful for minor mergers and at high redshifts.