CANGAROO-III search for TeV gamma-rays from two clusters of galaxies

木内, 隆太, 森, 正樹, 榎本, 良治, 郡司, 修一, 原, 忠生, Kiuchi, Ryuta, Mori, Masaki, Bicknell, G. V., Clay, R. W., Edwards, P. G., Enomoto, Ryoji, Gunji, Shuichi, Hara, S., Hara, Tadao, Hattori, T.

Astrophysics with All-Sky X-Ray observations: 3rd International MAXI Workshop (RIKEN, 10-12 June 2008)

As 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. Recently, a prediction was presented for gamma-ray emission from a cluster of galaxies at a detectable level with modern imaging atmospheric Cherenkov telescopes. The gamma-ray emission was produced via inverse Compton upscattering of cosmic microwave background (CMB) photons by electron-positron pairs generated by collisions of UHE cosmic rays in the cluster. We have 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. By comparing the upper limit for the north-west radio relic region of Abell 3667 with the model prediction, we can derive a lower limit of the magnetic field of the region of ca. 0.1 microG. This shows the potential of gamma-ray observations in studies of the cluster environment. We also discuss the upper limit from cluster center regions with a model of gamma-ray emission from neutral pion produced in hadronic collisions of cosmic-ray protons with the intra-cluster medium (ICM). The derived upper limit of the cosmic-ray energy density within this framework was one order higher than that of our Galaxy.

著者人数: 50人

Physical characteristics: Original contains color illustrations

資料番号: AA0064306065

レポート番号: JAXA-SP-08-014E

CANGAROO-III search for TeV gamma-rays from two clusters of galaxies

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CANGAROO-III search for TeV gamma-rays from two clusters of galaxies

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収録刊行物

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