title: Fermi bubbles: giant, multibillion-year-old reservoirs of Galactic center cosmic rays.
abstract: Recently evidence has emerged for enormous features in the γ-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 from the Galactic plane. These structures are coincident with a nonthermal microwave "haze" and an extended region of x-ray emission. The bubbles' γ-ray emission is characterized by a hard and relatively uniform spectrum, relatively uniform intensity, and an overall luminosity 4×10(37)   erg/s, around 1 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 time scale (≳ 8 Gyr) and high areal density star formation in the Galactic center.
authors.affiliation: Max-Planck-Institut für Kernphsik, P.O. Box 103980 Heidelberg, Germany. Roland.Crocker@mpi-hd.mpg.de
authors.forename: Roland M
authors.initials: RM
authors.lastname: Crocker
authors.forename: Felix
authors.initials: F
authors.lastname: Aharonian