Fermi Bubbles: Black Hole Activity or Large-Scale Bipolar Galactic Wind?

The Fermi LAT sky maps reveal two large gamma-ray lobes, extending 50 degrees above and below the Galactic center, with a width of about 40 degrees in longitude. These structures were likely created by some large episode of energy injection in the Galactic center, such as a large-scale accretion event onto the central black hole, or a nuclear starburst in the last 10 Myr. The gamma-ray signal is likely associated with the WMAP microwave excess known as the microwave haze. ROSAT X-ray maps at 1.5 keV show some similar features.

I will describe the spatial morphology of the fermi bubbles, and show that their energy spectrum is harder than other gamma-ray components in the inner Galaxy. The X-ray and microwave signals also have a hard spectrum, providing clues about their origin.

By understanding the origin and evolution of these structures, we will learn about recent energetic events in the inner Galaxy, and also improve our understanding of the diffuse Galactic gamma-ray emission, and the high-latitude cosmic ray population.