C Itoh, R Enomoto, S Yanagita, T Yoshida, A Asahara, G.V Bicknell, R.W Clay P.G Edwards, R Enomoto, S Gunji, S Hara, T Hara, T Hattori, Shin. Hayashi, Sei. Hayashi, S Kabuki, F Kajino, H Katagiri, J Kataoka, A Kawachi, T Kifune, H Kubo, J Kushida, Y Matsubara, Y Mizumoto, M Mori, H Moro, H Muraishi, Y Muraki, T Naito, T Nakase, D Nishida, K Nishijima, K Okumura, M Ohishi, J.R Patterson, R.J Protheroe, K Sakurazawa, D.L Swaby, T Tanimori, F Tokanai, K Tsuchiya, H Tsunoo, T Uchida, A Watanabe, S Yanagita, and T Yoshikoshi
The CANGAROO-II telescope observed sub-TeV gamma-ray emission from the nearby starburst galaxy NGC 253. The emission region was extended with a radial size of 0.3-0.6 degree. On the contrary, H.E.S.S could not confirm this emission and gave upper limits at the level of the CANGAROO-II flux. In order to resolve this discrepancy, we analyzed new observational results for NGC 253 by CANGAROO-III and also assessed the results by CANGAROO-II. Observation was made with three telescopes of the CANGAROO-III in October 2004. We analyzed three-fold coincidence data by the robust Fisher Discriminant method to discriminate gamma ray events from hadron events. The result by the CANGAROO-III was negative. The upper limit of gamma ray flux was 5.8% Crab at 0.58 TeV for point-source assumption. In addition, the significance of the excess flux of gamma-rays by the CANGAROO-II was lowered to less than 4 sigma after assessing treatment of malfunction of photomultiplier tubes.