CANGAROO-III SEARCH FOR TeV GAMMA RAYS FROM TWO CLUSTERS OF GALAXIES

Journal Article · Sat Oct 10 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/704/1/240· OSTI ID:21367445

Kiuchi, R; Mori, M; Enomoto, R; Kifune, T ^[1]; Bicknell, G V ^[2]; Clay, R W ^[3]; Edwards, P G ^[4]; Gunji, S; Inoue, K ^[5]; Hara, S; Itoh, C ^[6]; Hara, T ^[7]; Hattori, T; Kawachi, A ^[8]; Hayashi, S; Kajino, F ^[9]; Higashi, Y; Kabuki, S ^[10]; Hirai, Y ^[11]; Katagiri, H ^[12]

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1. Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan)
2. Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia)
3. School of Chemistry and Physics, University of Adelaide, SA 5005 (Australia)
4. CSIRO Australia Telescope National Facility, Narrabri, NSW 2390 (Australia)
5. Department of Physics, Yamagata University, Yamagata City, Yamagata 990-8560 (Japan)
6. Ibaraki Prefectural University of Health Sciences, Ami, Ibaraki 300-0394 (Japan)
7. Faculty of Management Information, Yamanashi Gakuin University, Kofu, Yamanashi 400-8575 (Japan)
8. Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292 (Japan)
9. Department of Physics, Konan University, Kobe, Hyogo 658-8501 (Japan)
10. Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
11. Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan)
12. Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

Because accretion and merger shocks in clusters of galaxies may accelerate particles to high energies, clusters are candidate sites for the origin of ultra-high-energy (UHE) cosmic rays. A prediction was presented for gamma-ray emission from a cluster of galaxies at a detectable level with the current generation of imaging atmospheric Cherenkov telescopes. The gamma-ray emission was produced via inverse Compton upscattering of cosmic microwave background photons by electron-positron pairs generated by collisions of UHE cosmic rays in the cluster. We observed two clusters of galaxies, Abell 3667 and Abell 4038, searching for very high energy gamma-ray emission with the CANGAROO-III atmospheric Cherenkov telescope system in 2006. The analysis showed no significant excess around these clusters, yielding upper limits on the gamma-ray emission. From a comparison of the upper limit for the northwest radio relic region of Abell 3667 with a model prediction, we derive a lower limit for the magnetic field of the region of approx0.1 muG. This shows the potential of gamma-ray observations in studies of the cluster environment. We also discuss the flux upper limit from cluster center regions using a model of gamma-ray emission from neutral pions produced in hadronic collisions of cosmic-ray protons with the intracluster medium. The derived upper limit of the cosmic-ray energy density within this framework is an order of magnitude higher than that of our Galaxy.

• OSTI ID: 21367445
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 704; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARYONS
BOSONS
COSMIC RADIATION
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
EMISSION
ENERGY DENSITY
ENERGY RANGE
FERMIONS
GALAXIES
GALAXY CLUSTERS
GAMMA RADIATION
HADRONS
IONIZING RADIATIONS
LEPTONS
MAGNETIC FIELDS
MASSLESS PARTICLES
MATTER
MESONS
MICROWAVE RADIATION
NUCLEONS
PHOTON EMISSION
PHOTONS
PIONS
PIONS NEUTRAL
POSITRONS
PROTONS
PSEUDOSCALAR MESONS
RADIATIONS
RELICT RADIATION
TELESCOPES
TEV RANGE