Detection of diffuse TeV gamma-ray emission from the nearby starburst galaxy NGC 253

(Astron. Astrophys. 396, L1-L4, 2002)

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

We report the TeV gamma-ray observations of the nearby normal spiral galaxy NGC 253. At a distance of ~2.5 Mpc, NGC 253 is one of the nearest starburst galaxies. This relative closeness, coupled with the high star formation rate in the galaxy, make it a good candidate TeV gamma-ray source. Observations were carried out in 2000 and 2001 with the CANGAROO-II 10 m imaging atmospheric Cerenkov telescope. TeV gamma-ray emission is detected at the ~11 sigma level with a flux of (7.8 +- 2.5) x 10-12 cm-2 sec-1 at energies >0.5 TeV. The data indicate that the emission region is broader than the point spread function of our telescope.