Astrophys. J., 802, 91 (2015/April-1)
Suzaku X-ray observations of the Fermi bubbles: northernmost cap and southeast claw discovered with MAXI-SSC.
TAHARA M., KATAOKA J., TAKEUCHI Y., TOTANI T., SOFUE Y., HIRAGA J.S., TSUNEMI H., INOUE Y., KIMURA M., CHEUNG C.C. and NAKASHIMA S.
Abstract (from CDS):
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 'deg) 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.
acceleration of particles - cosmic rays - Galaxy: halo - X-rays: ISM
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