The Fermi Bubbles: Giant, Multi-Billion-Year-Old Reservoirs of Galactic
  Center Cosmic Rays
  Recently evidence has emerged for enormous features in the gamma-ray sky
observed by the Fermi-LAT instrument: bilateral `bubbles' of emission centered
on the core of the Galaxy and extending to around 10 kpc above and below the
Galactic plane. These structures are coincident with a non-thermal microwave
`haze' found in WMAP data and an extended region of X-ray emission detected by
ROSAT. The bubbles' gamma-ray emission is characterised by a hard and
relatively uniform spectrum, relatively uniform intensity, and an overall
luminosity ~4 x 10^37 erg/s, around one order of magnitude larger than their
microwave luminosity while more than order of magnitude less than their X-ray
luminosity. Here we show that the bubbles are naturally explained as due to a
population of relic cosmic ray protons and heavier ions injected by processes
associated with extremely long timescale (>~8 Gyr) and high areal density
star-formation in the Galactic center.
