Colloquium – Atreya Acharyya – Astronomy at the Highest Photon Energies

Speaker: Dr.Atreya Acharyya (University of Alabama)

Astronomy at the Highest Photon Energies

Abstract:

Most astronomical telescopes observe thermal radiation. However, this does not include the most energetic gamma-rays photons, produced by large particle accelerators in space, which also act as tracers for cosmic-ray sources. While gamma-rays can be observed using space-based detectors, their relatively small effective area leads to a reduced sensitivity at the highest energies, typically above a few hundred GeV. This is also the energy regime in which ground-based telescopes become important in conducting a study of the Cherenkov radiation produced by the most energetic photons on entering the Earth’s atmosphere. In this colloquium, I present an overview of gamma-ray astronomy, beginning with the emission processes, current instruments and source classes observed. I then move on to the scientific potential of the discoveries, in particular those relating to active galactic nuclei, including addressing questions in astrophysics and fundamental physics and the important relation of gamma-rays to other cosmic messengers such as neutrinos before concluding with an overview of the next generation gamma-ray observatory, the Cherenkov Telescope Array.