A Tale of Cosmic Rays Narrated in G Rays by Fermi
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| Formato: | Artículo científico |
| Lenguaje: | en |
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Sociedade Brasileira de Física
2014
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| _version_ | 1876488314210484224 |
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| author | Luigi Tibaldo |
| author_facet | Luigi Tibaldo |
| contents | A Tale of Cosmic Rays Narrated in G Rays by Fermi Luigi Tibaldo Fermi LAT Física, Astronomía y Matemáticas Galaxies Milky Way Cosmic rays Superbubbles Diffuse emission Because cosmic rays are charged particles scrambled by magnetic fields, combining direct measurements with other observations is crucial to understanding their origin and propagation. As energetic particles traverse matter and electromagnetic fields, they leave marks in the form of neutral interaction products. Among those, γ rays trace interactions of nuclei that inelastically collide with interstellar gas, as well as of leptons that undergo Bremsstrahlung and inverse-Compton scattering. Data collected by the Fermi large area telescope (LAT) are therefore telling us the story of cosmic rays along their journey from sources through their home galaxies. Supernova remnants emerge as a notable γ-ray source population, and older remnants interacting with interstellar matter finally show strong evidence of the presence of accelerated nuclei. Yet the maximum energy attained by shock accelerators is poorly constrained by observations. Cygnus X, a massive star-forming region established by the LAT as housing cosmic-ray sources, provides a test case to study the impact of wind-driven turbulence on the early propagation. Interstellar emission resulting from the large-scale propagation of cosmic rays in the Milky Way is revealed in unprecedented detail that challenges some of the simple assumptions used for the modeling. Moreover, the cosmic-ray induced γ-ray luminosities of galaxies-scale quasi-linearly with their massive-star formation rates: the overall normalization of that relation below the calorimetric limit suggests that for most systems, a substantial fraction of energy in cosmic rays escapes into the intergalactic medium. The nuclear production models and the distribution of target gas and radiation fields, not determined precisely enough yet, are key to exploiting the full potential of γ-ray data. Nevertheless, data being collected by Fermi and complementary multiwavelength/multimessenger observations are bringing us ever closer to solving the cosmic-ray mystery. 2014 artículo científico 0103-9733 https://www.redalyc.org/articulo.oa?id=46432476019 en http://www.redalyc.org/revista.oa?id=464 Brazilian Journal of Physics application/pdf Sociedade Brasileira de Física Brazilian Journal of Physics (Brasil) Num.5 Vol.44 |
| format | Artículo científico |
| id | redalyc_46432476019 |
| institution | Redalyc |
| language | en |
| publishDate | 2014 |
| publisher | Sociedade Brasileira de Física |
| spellingShingle | A Tale of Cosmic Rays Narrated in G Rays by Fermi Luigi Tibaldo Física, Astronomía y Matemáticas Galaxies Milky Way Cosmic rays Superbubbles Diffuse emission A Tale of Cosmic Rays Narrated in G Rays by Fermi Luigi Tibaldo Fermi LAT Física, Astronomía y Matemáticas Galaxies Milky Way Cosmic rays Superbubbles Diffuse emission Because cosmic rays are charged particles scrambled by magnetic fields, combining direct measurements with other observations is crucial to understanding their origin and propagation. As energetic particles traverse matter and electromagnetic fields, they leave marks in the form of neutral interaction products. Among those, γ rays trace interactions of nuclei that inelastically collide with interstellar gas, as well as of leptons that undergo Bremsstrahlung and inverse-Compton scattering. Data collected by the Fermi large area telescope (LAT) are therefore telling us the story of cosmic rays along their journey from sources through their home galaxies. Supernova remnants emerge as a notable γ-ray source population, and older remnants interacting with interstellar matter finally show strong evidence of the presence of accelerated nuclei. Yet the maximum energy attained by shock accelerators is poorly constrained by observations. Cygnus X, a massive star-forming region established by the LAT as housing cosmic-ray sources, provides a test case to study the impact of wind-driven turbulence on the early propagation. Interstellar emission resulting from the large-scale propagation of cosmic rays in the Milky Way is revealed in unprecedented detail that challenges some of the simple assumptions used for the modeling. Moreover, the cosmic-ray induced γ-ray luminosities of galaxies-scale quasi-linearly with their massive-star formation rates: the overall normalization of that relation below the calorimetric limit suggests that for most systems, a substantial fraction of energy in cosmic rays escapes into the intergalactic medium. The nuclear production models and the distribution of target gas and radiation fields, not determined precisely enough yet, are key to exploiting the full potential of γ-ray data. Nevertheless, data being collected by Fermi and complementary multiwavelength/multimessenger observations are bringing us ever closer to solving the cosmic-ray mystery. 2014 artículo científico 0103-9733 https://www.redalyc.org/articulo.oa?id=46432476019 en http://www.redalyc.org/revista.oa?id=464 Brazilian Journal of Physics application/pdf Sociedade Brasileira de Física Brazilian Journal of Physics (Brasil) Num.5 Vol.44 |
| title | A Tale of Cosmic Rays Narrated in G Rays by Fermi |
| topic | Física, Astronomía y Matemáticas Galaxies Milky Way Cosmic rays Superbubbles Diffuse emission |
| url | https://www.redalyc.org/articulo.oa?id=46432476019 |