VHE gamma-ray astronomy experiments in India - Imaging cerenkov technique

Abstract

The recent advances in the field of very high energy (VHE) or TeV gamma-ray astronomy, culminating in the unambiguous detection of several galactic and extragalactic sources, owes itself largely to the successful exploitation of the Cerenkov imaging technique in the mono-and stereo operation modes. In this method, substantially improved detection sensitivities are achieved by recording the two - dimensional Cerenkov light distribution patterns in the focal plane of one or more light collectors and rejecting ? 99% background cosmic ray - initiated events on the basis of their distinct image shape and orientation characteristic. In the present communication, we describe the basic methodology of the Cerenkov imaging technique, particularly in the context of the TACTIC and MACE imaging systems, which are being set up by our group at Mt. Abu, India. The special design features of these two systems and the astrophysical problems likely to be addressed by them will be highlighted in this review.