Galactic Centre hypershell model for the North Polar Spurs

Abstract

The bipolar-hyper shell (BHS) model for the North Polar Spurs (NPS-E, -W, and\nLoop I) and counter southern spurs (SPS-E and -W) is revisited based on\nnumerical hydrodynamical simulations. Propagations of shock waves produced by\nenergetic explosive events in the Galactic Center are examined. Distributions\nof soft X-ray brightness on the sky at 0.25, 0.7, and 1.5 keV in a +/-50 deg x\n+/-50 deg region around the Galactic Center are modeled by thermal emission\nfrom high-temperature plasma in the shock-compressed shell considering\nshadowing by the interstellar HI and H2 gases. The result is compared with the\nROSAT wide field X-ray images in R2, 4 and 6 bands. The NPS and southern spurs\nare well reproduced by the simulation as shadowed dumbbell-shaped shock waves.\nWe discuss the origin and energetics of the event in relation to the starburst\nand/or AGN activities in the Galactic Center. [ High resolution pdf is\navailable at http://www.ioa.s.u-tokyo.ac.jp/~sofue/htdocs/2016bhs/ ]\n