Cosmic-ray propagation under consideration of a spatially resolved source distribution
August 09, 2023
The different elements of the interstellar medium have been continuously sampled through direct and indirect measurements of various messengers, such as cosmic rays (CRs). In addition to observations, numerical simulations of CR propagation, in particular diffuse transport, contribute to understanding the corresponding $\gamma$-ray emission components as seen by several experiments. Up to now, the standard approach for modeling source distributions used as input of such transport simulations mostly relies on radial symmetry and analytical functions rather than individual, observation-based sources. We present a redefinition of existing CR source distributions by combining sources observed with the High Energy Stereoscopic System telescope array (H.E.S.S.) and a simulated source distribution, which follows the matter density in the Milky Way. As a result, H.E.S.S.-inspired Galactic CR source distributions are inferred. We use the PICARD code to perform 3D-simulations of particle statistics in CR propagation using our hybrid source distribution models. This implementation of a three-dimensional source model based on observations and simulations enables highly resolved propagation modeling. It opens the path for more realistic CR transport scenarios beyond radial symmetry and delivers improved results in both the arm and interarm regions of the Galaxy. Furthermore, it provides an enhanced picture of the Galactic $\gamma$-ray sky including structures from our source model as well as the introduced gas distributions.
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