Giant gamma-ray bubbles from Fermi-LAT: active galactic nucleus activity or bipolar galactic wind?

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Giant gamma-ray bubbles from Fermi-LAT: active galactic nucleus activity or bipolar galactic wind?

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Title: Giant gamma-ray bubbles from Fermi-LAT: active galactic nucleus activity or bipolar galactic wind?
Author: Su, Meng; Slatyer, Tracy R.; Finkbeiner, Douglas

Note: Order does not necessarily reflect citation order of authors.

Citation: Su, Meng, Tracy R. Slatyer, and Douglas P. Finkbeiner. 2010. “Giant gamma-ray bubbles from Fermi-LAT: active galactic nucleus activity or bipolar galactic wind?” The Astrophysical Journal 724 (2) (November 10): 1044–1082. doi:10.1088/0004-637x/724/2/1044.
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Abstract: Data from the Fermi-LAT reveal two large gamma-ray bubbles, extending 50° above and below the Galactic center (GC), with a width of about 40° in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum (dN/dE ~ E –2) than the inverse Compton emission from electrons in the Galactic disk, or the gamma rays produced by the decay of pions from proton-interstellar medium collisions. There is no significant spatial variation in the spectrum or gamma-ray intensity within the bubbles, or between the north and south bubbles. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; the edges of the bubbles also line up with features in the ROSAT X-ray maps at 1.5-2 keV. We argue that these Galactic gamma-ray bubbles were most likely created by some large episode of energy injection in the GC, such as past accretion events onto the central massive black hole, or a nuclear starburst in the last ~10 Myr. Dark matter annihilation/decay seems unlikely to generate all the features of the bubbles and the associated signals in WMAP and ROSAT; the bubbles must be understood in order to use measurements of the diffuse gamma-ray emission in the inner Galaxy as a probe of dark matter physics. Study of the origin and evolution of the bubbles also has the potential to improve our understanding of recent energetic events in the inner Galaxy and the high-latitude cosmic ray population.
Published Version: doi:10.1088/0004-637X/724/2/1044
Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA
Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:33461909
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