Gamma-Rays and the Far-Infrared–Radio Continuum Correlation Reveal a Powerful Galactic Centre Wind

We consider the thermal and non-thermal emission from the inner 200 pc of the Galaxy. The radiation from this almost star-burst-like region is ultimately driven dominantly by on-going 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 power-ful (400-1200 km/s) 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. Key words: cosmic rays – ISM: jets and outflows – supernova remnants – Galaxy: centre – radio continuum: ISM – gamma-rays: theory