[https://doi.org/10.1051/0004-6361:20030247]
[https://doi.org/10.1051/0004-6361:20021565]
Issue |
A&A
Volume 462, Number 1, January IV 2007
|
|
---|---|---|
Page(s) | 67 - 71 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20066244 | |
Published online | 11 October 2006 |
Evidence of TeV gamma-ray emission from the nearby 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 e-mail: enomoto@icrr.u-tokyo.ac.jp
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
Received:
14
August
2006
Accepted:
29
September
2006
Aims.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, HESS 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.
Methods.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.
Results. 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.
Key words: gamma rays: observations / galaxies: starburst / galaxies: individual: NGC 253 / galaxies: halos
© ESO, 2007
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