Y. Higashi, H. Kubo, T. Yoshida, R. Enomoto, T. Tanimori, P. G. Edwards, T. Naito, G. V. Bicknell, R. W. Clay, S. Gunji, S. Hara, T. Hara, T. Hattori, S. Hayashi, Y. Hirai, K. Inoue, S. Kabuki, F. Kajino, H. Katagiri, A. Kawachi, T. Kifune, R. Kiuchi, J. Kushida, Y. Matsubara, T. Mizukami, Y. Mizumoto, R. Mizuniwa, M. Mori, H. Muraishi, Y. Muraki, T. Nakamori, S. Nakano, D. Nishida, K. Nishijima, M. Ohishi, Y. Sakamoto, A. Seki, V. Stamatescu, T. Suzuki, D. L. Swaby, G. Thornton, F. Tokanai, K. Tsuchiya, S. Watanabe, Y. Yamada, E. Yamazaki, S. Yanagita, T. Yoshikoshi, and Y. Yukawa
We observed the unidentified TeV gamma-ray source HESS J1804-216 with the CANGAROO-III atmospheric Cerenkov telescopes from May to July in 2006. We detected very high energy gamma rays above 600 GeV at the 10&sigma level in an effective exposure of 76 hr. We obtained a differential flux of (5.0 +- 1.5stat +- 1.6sys) × 1012(E/1 TeV)-&alphacm-2s-1TeV-1 with a photon index &alpha of 2.69 +- 0.30stat +- 0.34sys, which is consistent with that of the H.E.S.S. observation in 2004. We also confirm the extended morphology of the source. By combining our result with multi-wavelength observations, we discuss the possible counterparts of HESS J1804-216 and the radiation mechanism based on leptonic and hadronic processes for a supernova remnant and a pulsar wind nebula.