A new template background estimate for source searching in TeV -ray astronomy

A new method is described that permits quickly and easily, a 2-dimensional search for TeV (gamma)-ray sources over large fields of view (~ 6(degree)) with instruments utilising the imaging atmospheric Cerenkov technique. It employs as a background estimate, events normally rejected according to a cosmic-ray background rejection criterion based on image shape, but with reconstructed directions overlapping the source of interest. This so-called template background model is demonstrated using example data taken with the stereoscopic HEGRA System of Cerenkov Telescopes. Discussion includes comparisons with a conventional background estimate and limitations of the model. The template model is well suited to the search for point-like, moderately extended sources and combinations thereof, and compensates well for localised systematic changes in cosmic-ray background response.