Bipolar Hypershell Galactic Center Starburst Model: Further Evidence fromROSATData and New Radio and X‐Ray Simulations

Abstract

Using the all-sky ROSAT soft X-ray and 408 MHz radio continuum data, we show that the North Polar Spur (NPS) and its western and southern counterspurs draw a giant dumbbell shape necked at the Galactic plane. We interpret these features as due to a shock front originating from a starburst 15 million years ago with a total energy of the order of ~1056 ergs or 105 Type II supernovae. We simulate all-sky distributions of radio continuum and soft X-ray intensities based on the bipolar hypershell Galactic center starburst model. The simulations can well reproduce the radio NPS and related spurs, as well as radio spurs in the tangential directions of spiral arms. Simulated X-ray maps in the 0.25, 0.75, and 1.5 keV bands reproduce the ROSAT X-ray NPS, its western and southern counterspurs, and the absorption layer along the Galactic plane. We propose to use the ROSAT all-sky maps to probe the physics of gas in the halo-intergalactic interface, and to directly date and measure the energy of a recent Galactic center starburst.