FERMI BUBBLE γ-RAYS AS A RESULT OF DIFFUSIVE INJECTION OF GALACTIC COSMIC RAYS

Recently, the Fermi Space Telescope discovered two large gamma -ray emission regions, the so-called Fermi bubbles, that extend up to ~50[degrees] above and below the Galactic center (GC). The gamma -ray emission from the bubbles is found to follow a hard spectrum with no significant spatial variatio...

Full description

Saved in:
Bibliographic Details
Published in:Astrophysical journal. Letters 2013-11, Vol.778 (1), p.1-5
Main Author: THOUDAM, SATYENDRA
Format: Article
Language:English
Subjects:
ACCELERATION
Astroparticle Physics
Astropartikelfysik
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BUBBLES
COSMIC GAMMA SOURCES
COSMIC NUCLEI
COSMIC PHOTONS
COSMIC RAY PROPAGATION
cosmic rays
DIFFUSION
Electron acceleration
Emission
EMISSION SPECTRA
Galactic winds
galaxies
Galaxy
GAMMA RADIATION
gamma rays
halo
High speed
Inelastic collisions
INJECTION
LUMINOSITY
MILKY WAY
PARTICLE PRODUCTION
PLASMA
Spectral emissivity
STOCHASTIC PROCESSES
TELESCOPES
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Recently, the Fermi Space Telescope discovered two large gamma -ray emission regions, the so-called Fermi bubbles, that extend up to ~50[degrees] above and below the Galactic center (GC). The gamma -ray emission from the bubbles is found to follow a hard spectrum with no significant spatial variation in intensity and spectral shape. The origin of the emission is still not clearly understood. Suggested explanations include the injection of cosmic-ray (CR) nuclei from the GC by high-speed Galactic winds, electron acceleration by multiple shocks, and stochastic electron acceleration inside the bubbles. In this Letter, it is proposed that the gamma -rays may be the result of diffusive injection of Galactic CR protons during their propagation through the Galaxy. Considering that the bubbles are slowly expanding, and CRs undergo much slower diffusion inside the bubbles than in the average Galaxy and at the same time suffer losses due to adiabatic expansion and inelastic collisions with the bubble plasma, this model can explain the observed intensity profile, the emission spectrum and the measured luminosity without invoking any additional particle production processes, unlike other existing models.
ISSN:2041-8205
2041-8213
2041-8213
DOI:10.1088/2041-8205/778/1/L20