Colloquium: Dr. Tonia Venters, NASA

Energetic particles are ubiquitous in the cosmos and play a vital role in the cultivation of cosmic environments on all scales. Our pursuit of more than a century to uncover the origins and fate of these cosmic energetic particles has given rise to some of the most interesting and challenging questions in astrophysics. At sub-PeV energies, cosmic rays in star-forming galaxies can substantially influence galaxy properties linked to its formation and evolution; however, in order to assess the role of cosmic rays in cultivating galactic environments, we need to better understand their complex interplay with galaxy interstellar media and magnetic fields. At ultra-high energies, cosmic rays are the messengers of the most extreme physics in the cosmos; however, efforts to identify their origins have thus far been thwarted by the fact that they don’t point back to their sources. At both energy scales, multi-messenger observations of the byproducts of cosmic ray interactions could be the key to unraveling their mysteries. In this talk, I will discuss the recent observations in X-rays and gamma-rays of non-thermal emission in starburst galaxies and the implications these results have for these galaxies’ cosmic ray populations. On the ultra-high energy front, I will discuss how measurements of Earth-skimming neutrinos will be used to determine the composition of ultra-high energy cosmic rays and the evolution of their sources. In both cases, I will set the stage for next generation high-energy and ultra-high energy facilities.