PoS - Proceedings of Science
Volume 444 - 38th International Cosmic Ray Conference (ICRC2023) - Gamma-ray Astronomy (GA)
The local cosmic-ray spectrum probed by gamma-ray observations
G. Peron* and S. Gabici
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Pre-published on: July 25, 2023
Published on:
We propose a new sampling of the local ($\lesssim$2 kpc) cosmic-ray (CR) spectrum based on Fermi-LAT analysis of molecular clouds (MCs), for which we have a new improved distance estimation based on GAIA observations. The spatial and spectral distribution of CRs can effectively be proven by observing the gamma rays that they produce while interacting with the interstellar medium (ISM). In particular, the interactions of CR nuclei with the interstellar gas produce a gamma-ray flux which depends only on the CR spectrum at the location of the interaction and on the density of the target. Molecular clouds are small regions (10-100 pc) characterized by an enhanced gas density (n$\sim$100-1000 cm$^{-3}$) and hence they serve as perfect targets to localize and constrain CRs. The advent of GAIA revolutionized the understanding of the geometry of the local medium, providing a very precise three-dimensional mapping of the local dust. We extract the spectral energy distribution between a few hundred MeV to a few hundred GeV of a sample of clouds localized by GAIA in the local medium between 100 pc to 2 kpc. Investigating the local CR distribution is a fundamental step to understand if local propagation and/or acceleration effects are playing a role in shaping the observed CR spectrum that we measure at Earth.
DOI: https://doi.org/10.22323/1.444.0683
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