γ-rays and the far-infrared-radio continuum correlation reveal a powerful Galactic Centre wind

Abstract

We consider the thermal and non-thermal emission from the inner 200 pc of the Galaxy. The radiation from this almost starburst-like region is ultimately driven dominantly by ongoing massive star formation. We show that this region's radio continuum (RC) emission is in relative deficit with respect to the expectation afforded by the far-infrared-radio continuum correlation (FRC). Likewise we show that the region's γ -ray emission falls short of that expected given its star formation and resultant supernova rates. These facts are compellingly explained by positing that a powerful (400-1200 km s-1) wind is launched from the region. This wind probably plays a number of important roles including advecting positrons into the Galactic bulge thus explaining the observed ~kpc extension of the 511 keV positron annihilation signal around the GC. We also show that the large-scale GC magnetic field falls in the range ~100-300 μG and that - in the time they remain in the region - GC cosmic rays do not penetrate into the region's densest molecular material.