Study of initial acceleration mechanism of the Galactic cosmic-rays by the observation of the Galactic diffuse X-ray emission

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K14289
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Nara University of Education
• Principal Investigator: Nobukawa Masayoshi 奈良教育大学, 理科教育講座, 准教授 (00612582)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 銀河面拡散X線放射 / 低エネルギー宇宙線 / X線天文学 / 中性鉄輝線 / 超新星残骸 / X線天文衛星すざく / 銀河系中心

Outline of Final Research Achievements

This research focuses on the low energy band (~MeV) of the Galactic cosmic rays (LECRs). We measure the LECRs from supernova remnants (SNRs) with X-ray observation of the neutral Fe line at 6.4 keV. We found that the spacial distribution of the Fe line emission correlates with molecular gases, and hence the origin is possibly of LECRs. Observation of an SNR, IC443 with recombining plasmas revealed that ionization temperatures of heavy elements (Ne -- Ni) are different. It indicates that additional ionization is more likely than electron cooling as the origin of the recombining plasma. Also, we measured the plasma outflow with ~8 million K from the Galactic center, and discussed the origin.

Free Research Field

X線天文学

Academic Significance and Societal Importance of the Research Achievements

低エネルギー宇宙線の測定はこれまで困難であった。中性鉄輝線を用いた測定方法は、宇宙線の生成過程、すなわち宇宙線の起源を解明する上で重要な観測情報である。本研究では超新星残骸から低エネルギー宇宙線に由来する中性鉄輝線を初めて検出した。また、低エネルギー宇宙線が超新星残骸のプラズマに作用して、過電離状態にする可能性を示した。これらのことは超新星残骸、および宇宙線研究の新しい展開につながるだろう。