2021/04/30 by Guðlaugur Jóhannesson, Guđlaugur Jóhannesson, Troy A. Porter
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Cosmic ray #Dark Matter and Cosmic Phenomena #Fermi Gamma-ray Space Telescope #Gamma-ray bursts and supernovae #Interplanetary spaceflight #Interstellar medium #Particle acceleration #Range (aeronautics) #Sky #Spectral line #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/ac01c9
Accepted for publication by ApJ
openalex created_date 2021/05/10 · arxiv created 2021/05/15 · openalex publication_date 2021/08/01 · arxiv updated 2021/08/18 · openalex updated_date 2026/08/05
Abstract 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 localized 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 γ -ray sky. Using ∼10 yr 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°. 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 γ -ray emitter, and we also find significant emission from Loop I. Strong evidence is found for asymmetric features about the Galactic l = 0° meridian that may be associated with parts of the so-called “Fermi Bubbles,” and some evidence is also found for γ -ray emission from other radio loops. Implications for the CRs producing the features and possible locations of the sources of the emissions are discussed.