TeV γ-rays from old supernova remnants |
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Authors: | Ryo Yamazaki Kazunori Kohri Aya Bamba Tatsuo Yoshida Toru Tsuribe Fumio Takahara |
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Affiliation: | Department of Physics, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan;Institute for Theory and Computation, Harvard–Smithsonian Center for Astrophysics, MS-51, 60 Garden Street, Cambridge, MA 02138, USA;RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan;Faculty of Science, Ibaraki University, Mito 310-8512, Japan;Department of Earth and Space Science, Osaka University, Toyonaka 560-0043, Japan |
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Abstract: | We study the emission from an old supernova remnant (SNR) with an age of around 105 yr and that from a giant molecular cloud (GMC) encountered by the SNR. When the SNR age is around 105 yr, proton acceleration is efficient enough to emit TeV γ-rays both at the shock of the SNR and that in the GMC. The maximum energy of primarily accelerated electrons is so small that TeV γ-rays and X-rays are dominated by hadronic processes, π0 -decay and synchrotron radiation from secondary electrons, respectively. However, if the SNR is older than several 105 yr, there are few high-energy particles emitting TeV γ-rays because of the energy-loss effect and/or the wave-damping effect occurring at low-velocity isothermal shocks. For old SNRs or SNR–GMC interacting systems capable of generating TeV γ-ray emitting particles, we calculated the ratio of TeV γ-ray (1–10 TeV) to X-ray (2–10 keV) energy flux and found that it can be more than ∼102 . Such a source showing large flux ratio may be a possible origin of recently discovered unidentified TeV sources. |
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Keywords: | acceleration of particles shock waves ISM: clouds supernova remnants gamma-rays: theory X-rays: ISM |
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