Fermi Gamma-ray Space Telescope

Comparison between Fermi Bubble and Loop-I observed by MAXI/SSC

Masashi Kimura
H.Tomida,H.Tsunemi,D.Uchida,Y.Morooka

Abstract:

The Fermi Gamma-ray Space Telescope reveals two large gamma-ray bubbles in the Galaxy, which extend about 50 degrees above and below the Galactic center and are symmetric about the Galactic plane. There are several theories regarding the origins of these bubbles, such as AGN jet at the galactic center and star captured by central black hole. On the other hand, All sky map in soft X-ray(0.7-1.7keV) obtained by MAXI/SSC shows large diffuse structure in the direction of galactic center. This structure is called Loop-I and its radius is about 60 degrees. The origin of this structure is still unknown. Loop-I could be ordinary SNR which happened to be near (~100pc) from the sun or it could be much bigger structure located near the center of galaxy(~ 8kpc). Previous study shows that the Loop-I and the Fermi bubble shows some correlation. The brightest part of Loop-I, which is called North Polar Spur(NPS) is located just outside the rim of fermi bubble. We used data taken by MAXI/SSC and performed spectral analysis of Loop-I and detected Ne and Mg emission line which suggest that the Loop-I is thermal. We also found that the spectrum from this structure can be fitted by collisional ionization equilibrium model with temperature of 0.3keV. We will discuss the origin of this structure and comparison with Fermi bubble.