Diffuse x-ray emission from the northern arc of loop I observed with suzaku

Abstract

After discovery of the Fermi bubbles, giant structures observed in radio to X-rays have been discussed as possi- ble evidence of past activities in the Galactic Center (GC). We report here on the analysis of Suzaku data pointing around the Loop I arc. The diffuse X-ray emission 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. The temper- ature of the absorbed thermal plasma was clustered in a range of 0.30 +- 0.02 keV along Loop I ("ON" regions), whereas the temperature was about 20 % lower in the cavity adjacent to the bubbles and Loop I ("OFF" regions) with 0.24 +- 0.03 keV. The emission measure (EM) varied along the Galactic latitude, and was well correlated with the count rate variation as measured with the ROSAT in 0.75 keV band. Although the amount of neutral gas was not conclusive to constrain on the distance to Loop I, the observed EM values rule out a hypothesis that the structure is close to the Sun; we argue that the Loop I is a distant, kpc structure of the shock-heated GH gas. 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.

arXiv comment7 pages, 5 figures; accepted for publication in ApJ

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Cited by in corpus (9)

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• Thermal and chemical properties of the eROSITA bubbles from Suzaku observations
• Interaction of the Galactic-Centre Super Bubbles with the Gaseous Disc
• Asymmetric eROSITA bubbles as the evidence of a circumgalactic medium wind
• Analytical and numerical studies of central galactic outflows powered by tidal disruption events -- a model for the Fermi bubbles?
• Diagnostics of Gaseous Halo of the Milky Way by a Shock Wave from the Galactic Centre
• MAXI/SSC All-sky maps from 0.7 keV to 4 keV
• The Bending Feature of the Fermi Bubbles: A Presumed Horizontal Galactic Wind and Its Implication on the Bubbles' Age
• Discovery of non-equilibrium ionization plasma associated with the North Polar Spur and Loop I