Signatures of Recent Cosmic-Ray Acceleration in the High-Latitude -Ray Sky

Cosmic-ray (CR) sources temporarily enhance the relativistic particle density in their vicinity over the background distribution accumulated by the 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. The observation of large scale loop like structures in the radio sky is possible evidence of such nearby CR sources. If so, these loops should also be most visible in the high-latitude gamma-ray sky. Using similar to 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 deg. 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 toward the Galactic centre 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.