Kavli Affiliate: Troy A. Porter
| First 5 Authors: Guðlaugur Jóhannesson, Troy A. Porter, , ,
| Summary:
Cosmic-ray (CR) sources temporarily enhance the relativistic particle density
in their vicinity over the background distribution accumulated from the
Galaxy-wide past injection activity and propagation. If individual sources are
close enough to the solar system, their localised enhancements may present as
features in the measured spectra of the CRs and in the associated secondary
electromagnetic emissions. Large scale loop like structures visible in the
radio sky are possible signatures of such nearby CR sources. If so, these loops
may also have counterparts in the high-latitude $gamma$-ray sky. Using
$sim$10 years of data from the Fermi Large Area Telescope, applying Bayesian
analysis including Gaussian Processes, we search for extended enhanced emission
associated with putative nearby CR sources in the energy range from 1 GeV to 1
TeV for the sky region $|b| > 30^circ$. We carefully control the systematic
uncertainty due to imperfect knowledge of the interstellar gas distribution.
Radio Loop~IV is identified for the first time as a $gamma$-ray emitter and we
also find significant emission from Loop~I. Strong evidence is found for
asymmetric features about the Galactic $l = 0^circ$ meridian that may be
associated with parts of the so-called "Fermi Bubbles", and some evidence is
also found for $gamma$-ray emission from other radio loops. Implications for
the CRs producing the features and possible locations of the sources of the
emissions are discussed.
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