Universe Seen From Very High Energy Eyes

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With an imaging atmospheric Cherenkov telescope of 10m diameter in Woomera, Australia, which was expanded from a 7m telescope in 2000 and was jointly operated by a consortium of Japanese and Australian institutions, we observed very high-energy gamma-rays from active celestial objects such as supernovae, pulsars, active galactic nuclei in the southern hemisphere. The second, third and fourth telescopes were build in 2002, 2003 and 2004, respectively, and we started stereoscopic observation of Cherenkov light from gamma-ray showers. With the stereoscopic method, angular resolution and energy resolution of gamma-ray events are improved and discrimination of gamma-ray events from background cosmic-ray showers became better than single telescope observations.Although the array of four telescopes was completed in the last year of the term of the project, we have accumulated observational data including single and stereoscopic observations for five years. From the data 1)we have discovered high-energy gamma-ray signals from a supernova RX J0854.0-4622, a starburst galaxy NGC253 and the Galactic center, 2)we have confirmed our previous detection of supernovae RX J1713.7-3946 and SN1006 and a pulsar PSR 1704-44 and extended the observed spectrum, 3)we have detected the most energetic gamma-rays from an active galactic nucleus Mrk421, and 4)we have set upper limits on gamma-ray fluxes from a supernova SN1987A and a pulsar binary PSR 1259-64/SS2883. Our results are the key observations to reveal particle acceleration mechanism in the Universe, which is directly related to the long-standing problem of the origin of cosmic rays.