Measurement of the radial distribution of Cherenkov light generated by TeVgamma-ray air showers

Using air showers induced by TeV gamma-rays from Mrk 501, the radial distri bution of Cherenkov light is investigated. The shower geometry is reconstru cted from the stereoscopic shower images obtained with the telescopes of th e HEGRA IACT system. With the core position known to better than 10 m, the light yield as a function of the distance to the shower axis is derived by comparing event-by-event the image intensities measured in the different te lescopes. We observe a change in the shape of the light pool with zenith an gle, an a slow variation with show cr energy. Data are well reproduced by M onte Carlo air shower simulations. (C) 1999 Elsevier Science B.V.