GIANT GAMMA-RAY BUBBLES FROM FERMI-LAT: ACTIVE GALACTIC NUCLEUS ACTIVITY OR BIPOLAR GALACTIC WIND?
Data from the Fermi-LAT reveal two large gamma-ray bubbles, extending 50{sup 0} above and below the Galactic center (GC), with a width of about 40{sup 0} in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum (dN/dE {approx} E {sup -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 {approx}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.
- OSTI ID:
- 21474500
- Journal Information:
- Astrophysical Journal, Vol. 724, Issue 2; Other Information: DOI: 10.1088/0004-637X/724/2/1044; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ANNIHILATION
BLACK HOLES
COSMIC RADIATION
ELECTRONS
GALACTIC EVOLUTION
GALAXIES
GAMMA RADIATION
MICROWAVE RADIATION
NONLUMINOUS MATTER
PARTICLE DECAY
PIONS
PROTONS
BARYONS
BOSONS
DECAY
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EVOLUTION
FERMIONS
HADRONS
INTERACTIONS
IONIZING RADIATIONS
LEPTONS
MATTER
MESONS
NUCLEONS
PARTICLE INTERACTIONS
PSEUDOSCALAR MESONS
RADIATIONS