Diffuse X-Ray Emission from the Northern Arc of Loop i Observed with Suzaku

Masahiro Akita, Jun Kataoka, Makoto Arimoto, Yoshiaki Sofue, Tomonori Totani, Yoshiyuki Inoue, Shinya Nakashima

    研究成果: Article査読

    11 被引用数 (Scopus)


    After discovery of the Fermi bubbles, giant structures observed from radio to X-ray monitoring have been widely discussed as possible evidence of past activities in the Galactic center (GC). We report here on the analysis of all the Suzaku archival data pointing around the giant-scale Loop I arc. The diffuse X-ray emission from the northern Loop I arc was well represented by the three-component model: (1) an unabsorbed thermal plasma with kT ≃ 0.1 keV either from the local hot bubble (LHB) and/or solar wind charge exchange (SWCX), (2) an absorbed thermal plasma regarded as a contribution from the Loop I and the Galactic halo (GH), and (3) an absorbed power-law component representing the cosmic X-ray background (CXB). The temperature of the absorbed thermal plasma was narrowly clustered in a range of 0.30 ± 0.02 keV along Loop I ("ON" regions), whereas the temperature was a little lower in the cavity adjacent to the bubbles and Loop I ("OFF" regions) with 0.24 ± 0.03 keV. The emission measure (EM) largely varied along the Galactic latitude b, and was well correlated with the count rate variation as measured with the ROSAT all-sky map in 0.75 keV. Although the amount of neutral gas does not provide any useful constraints on the distance to Loop I, the observed EM values clearly reject a hypothesis that the structure is close to the Sun; we argue that Loop I is a distant, kiloparsec structure in the GH. We discuss the origin of apparent mismatch in the morphologies of the Fermi bubbles and the Loop I arc, suggesting a two-step explosion process in the GC.

    ジャーナルAstrophysical Journal
    出版ステータスPublished - 2018 7月 20

    ASJC Scopus subject areas

    • 天文学と天体物理学
    • 宇宙惑星科学


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