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第1458回 天文学教室談話会

日時

2016年07月11日(月) 15:00

場所

合同C棟大輪講

講演者

Sabrina Coudry(東北大学天文学専攻)

題目

Investigation of the magnetic field diffusion on the Fermi Bubbles features

要旨


The Fermi Bubbles (FB) are two giant gamma-ray structures extending to ~ 50°in the Galactic latitude, above and below the Galactic center (GC), with a width of ~40° in the Galactic longitude. They are spatially correlated with 23-60 GHz microwave emission measured by WMAP & Planck satellite, share edges with X-rays emission at 1.5 keV measured by the ROSAT telescope, and also associated with two giant radio polarized lobes at 2.3 GHz discovered by S-PASS survey. The main observational results are a uniform gamma-ray surface brightness with sharp edges, a hard spectrum energy distribution in 1< Eγ < 100GeV. Theoretical models and Simulation, constrained by these features, are principally based on the interaction between wind/jet from GC and interstellar medium (ISM). The origin of gamma ray photons is still under debate though, and several models are used to try to light up our understanding. So far, AGN jets, wind, or SNe driven models have been explored by numerical hydrodynamic or MHD simulation to understand the spatial distribution of the CRs & their spectrum. The magnetic field (and then anisotropic CRs diffusion along field lines) play indeed an important role in the interpretation of the sharpness of the observed surface brightness of the FB and on the confinement of the CRp in the hadronic model. In this study, we try to clarify the physical mechanisms of the global spatial structure and uniformity of the gamma-ray surface brightness of FB. The magnetic field and cosmic ray diffusions may play central role to determine these characteristics. As it has been widely known, the magnetic and cosmic ray diffusion coefficients in comic plasmas differ from the microscopically expected values and have been treated as unknown key parameters. Therefore, we are willing to study how the structure of the FB responds to magnetic and cosmic ray diffusion coefficients by performing 3D MHD simulation in which magnetic and cosmic ray diffusions are explicitly taken into account. For this purpose, we are developing a new HLL and HLLD Resistive MHD codes in which the cosmic diffusion are simultaneously solved.

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【The Colloquium Committee in 2016】
Kenji Toma (toma<at>astr.tohoku.ac.jp)
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