SUZAKU X-RAY OBSERVATIONS OF THE FERMI BUBBLES: NORTHERNMOST CAP AND SOUTHEAST CLAW DISCOVERED WITH MAXI-SSC

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° 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°, ) 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 keV. The temperature 0.3 keV of the GH is higher than the ubiquitous value of 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.