Daniele Gaggero, Carmelo Evoli, Dario Grasso, Luca Maccione
The Fermi-LAT collaboration recently confirmed EGRET finding of a discrepancy
between the observed longitudinal profile of gamma-ray diffuse emission from
the Galaxy and that computed with GALPROP assuming that cosmic rays are
produced by Galactic supernova remnants. The accurate Fermi-LAT measurements
make this anomaly hardly explainable in terms of conventional diffusion
schemes. Here we use DRAGON numerical diffusion code to implement a physically
motivated scenario in which the diffusion coefficient is spatially correlated
to the source density. We show that under those conditions we are able to
reproduce the observed flat emissivity profile in the outer Galaxy with no need
to change the source term, the diffusion halo height, or the CO-H2 conversion
factor (XCO) with respect to their preferred values/distributions. We also show
that our models are compatible with gamma-ray longitudinal profiles measured by
Fermi-LAT, and still provide a satisfactory fit of all observed
secondary-to-primary ratios, such as B/C and antiprotons/protons.
View original:
http://arxiv.org/abs/1111.1636
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