Physics & Astronomy Colloquium

3:30 PM, Friday, September 15, 2006

Room 155, Chem-Phys Building

Dr. Trevor Weekes

Harvard-Smithsonian Center for Astrophysics

``The Universe as seen in TeV Gamma Rays''

TeV gamma rays from cosmic sources can be seen from the ground using simple optical techniques to detect the Cherenkov radiation from their electromagnetic cascades in the earth's atmosphere. The trick is then to identify the Cherenkov gamma-ray events among the much more numerous background events from cosmic ray hadrons. The development of the atmospheric Cherenkov imaging technique, with which more than 30 cosmic sources have been detected, will be described. It was generally supposed that the cosmic radiation (at least at energies up to 100 TeV) originated in supernova remnants and that TeV gamma-ray astronomy would provide strong observational evidence for this hypothesis. In the past decade many cosmic TeV sources have been detected demonstrating that TeV gamma-ray emission is ubiquitous and not confined to supernova remnants. In particular many Active Galactic Nuclei have been detected. VERITAS, a next generation array of telescopes in southern Arizona, will be described.

Refreshments will be served in CP 179 at 3:15 PM