Physical Society Colloquium

Ultra-high-energy Cosmic-ray Astronomy and Astrophysics with the Pierre Auger Observatory

Vasiliki Pavlidou

Kavli Institute for Cosmological Physics
University of Chicago

The highest-energy cosmic rays are expected to be strongly attenuated through interactions with the cosmic microwave background (the GZK cutoff), so that such particles reaching the Earth must only be sampling the local, strongly anisotropic, universe volume. Recent results from the Pierre Auger Observatory probe the cosmic ray energy spectrum in the GZK cutoff regime; at the same time, the arrival directions of the highest-energy cosmic-ray events were shown to be anisotropic, and correlated with nearby extragalactic structure. These results are consistent with expectations for cosmic ray energy losses during cosmological propagation, are opening up the era of charged particle astrophysics and astronomy, and are providing a direct way to probe the sources of the highest-energy particles in the universe.