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Title: MULTI-WAVELENGTH EMISSION FROM THE FERMI BUBBLE. II. SECONDARY ELECTRONS AND THE HADRONIC MODEL OF THE BUBBLE

We analyze the origin of the gamma-ray flux from the Fermi Bubbles (FBs) in the framework of the hadronic model in which gamma-rays are produced by collisions of relativistic protons with the protons of the background plasma in the Galactic halo. It is assumed in this model that the observed radio emission from the FBs is due to synchrotron radiation of secondary electrons produced by pp collisions. However, if these electrons lose their energy through synchrotron and inverse-Compton emission, the spectrum of secondary electrons will be too soft, and an additional arbitrary component of the primary electrons will be necessary in order to reproduce the radio data. Thus, a mixture of the hadronic and leptonic models is required for the observed radio flux. It was shown that if the spectrum of primary electrons is ∝E{sub e}{sup −2}, the permitted range of the magnetic field strength is within the 2-7 μG region. The fraction of gamma-rays produced by pp collisions can reach about 80% of the total gamma-ray flux from the FBs. If the magnetic field is <2 μG or >7 μG the model is unable to reproduce the data. Alternatively, the electrons in the FBs may lose their energy throughmore » adiabatic energy losses if there is a strong plasma outflow in the GC. Then, the pure hadronic model is able to reproduce characteristics of the radio and gamma-ray flux from the FBs. However, in this case the required magnetic field strength in the FBs and the power of CR sources are much higher than those following from observations.« less
Authors:
; ;  [1] ;  [2]
  1. Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong (China)
  2. Institute of Astronomy, Department of Physics and Center for Complex Systems, National Central University, Jhongli, Taiwan (China)
Publication Date:
OSTI Identifier:
22364432
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 799; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; BUBBLES; COSMIC ELECTRONS; COSMIC PROTONS; COSMIC RADIO SOURCES; ENERGY LOSSES; GALAXIES; MAGNETIC FIELDS; MILKY WAY; PARTICLE MODELS; PLASMA; PROTON-PROTON INTERACTIONS; RELATIVISTIC RANGE; SYNCHROTRON RADIATION; WAVELENGTHS