Letter to the Editor

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

¹ Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan
² Institute for Cosmic Ray Research, Univ. of Tokyo, Kashiwa, Chiba 277-8582, Japan
³ Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
⁴ MSSSO, Australian National University, ACT 2611, Australia
⁵ Department of Physics and Math. Physics, University of Adelaide, SA 5005, Australia
⁶ Institute for Space and Aeronautical Science, Sagamihara, Kanagawa 229-8510, Japan
⁷ Department of Physics, Yamagata University, Yamagata, Yamagata 990-8560, Japan
⁸ Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
⁹ Faculty of Management Information, Yamanashi Gakuin University, Kofu,Yamanashi 400-8575, Japan
¹⁰ Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan
¹¹ Department of Physics, Konan University, Hyogo 658-8501, Japan
¹² Faculty of Engineering, Shinshu University, Nagano, Nagano 380-8553, Japan
¹³ STE Laboratory, Nagoya University, Nagoya, Aichi 464-8601, Japan
¹⁴ National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
¹⁵ Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Ibaraki 300-0394, Japan
¹⁶ Department of Physics, Osaka City University, Osaka, Osaka 558-8585, Japan

Corresponding author: R. Enomoto, enomoto@icrr.u-tokyo.ac.jp

Received: 9 September 2002
Accepted: 29 October 2002

Abstract

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 ~ level with a flux of at energies >0.5 TeV. The data indicate that the emission region is broader than the point spread function of our telescope.