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