Suzaku X-ray observations of the fermi bubbles: Northernmost cap and southeast claw discovered with MAXI-SSC

M. Tahara, Jun Kataoka, Y. Takeuchi, T. Totani, Y. Sofue, J. S. Hiraga, H. Tsunemi, Y. Inoue, M. Kimura, C. C. Cheung, S. Nakashima

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    13 Citations (Scopus)

    Abstract

    We report on Suzaku observations of large-scale X-ray structures possibly related to the Fermi Bubbles obtained in 2013 with a total duration of ≃80 ks. The observed regions were (1) the northern cap (N-cap; l ∼ 0°, 45° < b< 55°) seen in the mid-band (1.7-4.0 keV) map recently provided by Monitor of All-sky X-ray Image Solid-state Slit Camera (MAXI-SSC) and (2) the southeast claw (SE-claw; l ∼ 10°, -20° < b < -10°) seen in the ROSAT all-sky map and MAXI-SSC low-band (0.7-1.7 keV) map. In each region, we detected diffuse X-ray emission, which is represented by a three-component plasma model consisting of an unabsorbed thermal component (kT ≃ 0.1 keV) from the Local Hot Bubble, absorbed kT = 0.30 ± 0.05 keV emission representing the Galactic halo (GH), and a power-law component due to the isotropic cosmic X-ray background radiation. The emission measure of the GH component in the SE-claw shows an excess by a factor of ≃2.5 over the surrounding emission at 2° away. We also found a broad excess in the 1.7-4.0 keV count rates across the N-cap after compiling other archival data from Suzaku and Swift. The spectral stacking analysis of the N-cap data indicates the presence of another thermal component with kT = 0.70-0.11 +0.22keV. The temperature kT ≃ 0.3 keV of the GH is higher than the ubiquitous value of kT ≃ 0.2 keV near the Fermi bubbles, and can be even higher (∼0.7 keV). We discuss our findings in the context of the bubble-halo interaction.

    Original languageEnglish
    Article number91
    JournalAstrophysical Journal
    Volume802
    Issue number2
    DOIs
    Publication statusPublished - 2015 Apr 1

    Keywords

    • Acceleration of particles
    • Cosmic rays
    • Galaxy: Halo
    • X-rays: ISM

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

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    Tahara, M., Kataoka, J., Takeuchi, Y., Totani, T., Sofue, Y., Hiraga, J. S., Tsunemi, H., Inoue, Y., Kimura, M., Cheung, C. C., & Nakashima, S. (2015). Suzaku X-ray observations of the fermi bubbles: Northernmost cap and southeast claw discovered with MAXI-SSC. Astrophysical Journal, 802(2), [91]. https://doi.org/10.1088/0004-637X/802/2/91