cherenkov telescope array Origin and role of relativistic cosmic particles Contact authors: A. Araudo (LUMP - [email protected]), G. Morlino (INAF - [email protected]), B. Olmi (INAF - [email protected]) on behalf of the CTA Consortium. https://www.cta-observatory.org/about/cta-consortium/ Credit: CTA arXiv:2106.03599v2 [astro-ph.HE] 15 Jun 2021 This white paper briefly summarizes the importance of the study of relativistic cosmic rays, both as a constituent of our Universe, and through their impact on stellar and galactic evolution. The focus is on what can be learned over the coming decade through ground-based gamma-ray observations over the 20 GeV to 300 TeV range. The majority of the material is drawn directly from “Science with the Cherenkov Telescope Array” [1], which describes the overall science case for CTA. We request that authors wishing to cite results contained in this white paper cite the original work. Authors F. Acero (AIM, CEA, CNRS, Universite´ Paris-Saclay, Universite´ de Paris, France), I. Agudo (Instituto de Astrof´ısica de Andaluc´ıa-CSIC, Spain), R. Adam (Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS/IN2P3, 91128 Palaiseau, France), A. Araudo (LUPM, Montpellier), R. Alves Batista (Radboud University Nijmegen, Netherlands), E. Amato (INAF - Osservatorio Astrofisico di Arcetri, Italy), E.O. Anguner (Centre de Physique des Particules de Marseille, France), L. A. Antonelli (INAF-Osservatorio Astronomico di Roma, Italy), Y. Ascasibar (Universidad Autonoma´ de Madrid, Spain), C. Balazs (Monash University, Australia), J. Becker Tjus (Ruhr-Universitat¨ Bochum, 44780 Bochum, Germany), C. Bigongiari (INAF-Osservatorio Astronomico di Roma, Italy), E. Bissaldi (Politecnico and INFN Bari, Italy), J. Bol- mont (LPNHE, CNRS/IN2P3, Sorbonne University, France), C. Boisson (LUTH, Observatoire de Paris, France), P. Bordas (Universitat de Barcelona, ICCUB, IEEC-UB, Spain), Z.ˇ Bosnjakˇ (Zagreb University - FER, Croatia), A. M. Brown (Durham University) M. Burton (Armagh Observatory and Planetarium, UK) N. Bucciantini ( INAF-Osservatorio Astrofisico di Arcetri, Italy), F. Cangemi (LPNHE, CNRS, Sor- bonne University, France), P.Caraveo (INAF-IASF, Italy), M. Cardillo (INAF - IAPS, Roma, Italy), S. Caroff (LAPP,Univ. SMB, CNRS/IN2P3, France), S. Casanova (IFJ-PAN, Krakow, Poland), S. Chaty (University of Paris and CEA, France), M. Chernyakova (School of Physical Sciences and CfAR, Dublin City Univer- sity, Ireland), J. G. Coelho (UFPR - Universidade Federal do Parana, Brazil), F. Conte (MPI for Nuclear Physics, Heidelberg, Germany), G. Cotter (University of Oxford, UK), S. Crestan(Universita´ degli studi dell’Insubria, INAF-IASF Milano, Italy) A. D’A´ı (INAF - IASF Palermo, Italy), E. M. de Gouveia Dal Pino (IAG - Universidade de Sao Paulo, Brazil), C. Delgado (CIEMAT), D. della Volpe (Universite´ de Geneve,` Switzerland), D. de Martino (INAF-Osservatorio Astronomico di Capodimonte-Napoli, Italy), A. Djannati- Ata¨ı (Universite´ de Paris, CNRS/IN2P3, APC, France), R.C. Dos Anjos (UFPR - Universidade Federal do Parana,´ Brazil), V. Dwarkadas (University of Chicago, USA), G. Emery (Universite´ de Geneve,` Switzer- land), E. Fedorova (Taras Shevchenko National University of Kyiv, Ukraine), M. D. Filipovic (Western Sydney University, Australia), O. Fornieri (DESY Zeuthen), G. Galanti (INAF - IASF Milano, Italy), D. Gasparrini (INFN Roma Tor Vergata & ASI-SSDC, Italy), G. Ghirlanda (INAF-Osservatorio Astronomico di Brera, Italy), A. Giuliani (INAF - IASF Milano, Italy) P. Goldoni (APC/IRFU, France) J. Granot (Open University of Israel, P.O.B 808, Ra’anana 43537, Israel) D. Grasso (INFN, Pisa, Italy), E. de Ona˜ Wilhelmi (Desy-Zeuthen, Germany), B. Khelifi´ (APC, IN2P3/CNRS - Universite´ de Paris, France), M. Heller (Uni- versity of Geneva, Switzerland), D. Horan (LLR/Ecole Polytechnique, CNRS/IN2P3), B. Hnatyk (Taras Shevchenko National University of Kyiv, Ukraine), R. Hnatyk (Taras Shevchenko National University of Kyiv, Ukraine), S. Inoue (RIKEN, Japan), M. Jamrozy (Jagiellonian University, Poland), N. Komin (Univer- sity of the Witwatersrand, Johannesburg, South Africa), A. Lamastra (INAF-Osservatorio Astronomico di Roma, Italy), N. La Palombara (INAF - IASF Milano, Italy), J.-P.Lenain (LPNHE, CNRS/IN2P3, Sorbonne University, France), I. Liodakis (FINCA, University of Turku, Finland), S. Lombardi (INAF-Osservatorio Astronomico di Roma, Italy), F. Longo (University and INFN, Trieste, Italy), A. Lopez-Oramas´ (IAC & Universidad de La Laguna, Spain), M. Lopez-Moya´ (EMFTEL and IPARCOS, Universidad Complutense de Madrid, Spain), F. Lucarelli (INAF-Oss. Astr. Roma & ASI-SSDC, Italy), P. L. Luque-Escamilla (Uni- versidad de Jaen,´ Spain), P. Majumdar (Saha Institute of Nuclear Physics, Kolkata, India), A. Marcowith (Laboratoire Univers et Particules de Montpellier, France), J. Mart´ı (Universidad de Jaen,´ Spain), M. Martinez (Institut de F´ısica d’Altes Energies, IFAE-BIST, Barcelona, Spain), D. Mazin (ICRR, University of Tokyo, Japan and MPI for physics, Munich, Germany), S. Menchiari (Universita` degli studi di Siena, Italy), L. Mohrmann (FAU Erlangen-Nurnberg,¨ Germany), T. Montaruli (University of Geneva, Switzer- land), G. Morlino (INAF/Oss. Astrofisico di Arcetri, Italy), A. Morselli (INFN Roma Tor Vergata), C.G. Mundell (University of Bath, UK), T. Murach (DESY Zeuthen, Germany), A. Nagai (University of Geneva, Switzerland), A. Nayerhoda(Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland), J. Niemiec (Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland), M. Nikolajuk (University of Bialystok, Poland), B. Olmi (INAF/Oss. Astronomico di Palermo, Italy), R.A. Ong (Univer- sity of California, Los Angeles, CA, USA), J.M. Paredes (Universitat de Barcelona, ICCUB, IEEC-UB, Spain), G. Pareschi (INAF Osservatorio Astronomico di Brera), M. Pohl (University of Potsdam & DESY), G. Puhlhofer¨ (IAAT, University of Tubingen,¨ Germany), M. Punch (APC, IN2P3/CNRS - Universite´ de Paris, France), O. Reimer (Innsbruck University, Institute for Astro- and Particle Physics, Austria), M. Ribo´ (Universitat de Barcelona, ICCUB, IEEC-UB, Spain), F. Rieger (Max-Planck-Institut fur¨ Kernphysik, 69117 Heidelberg, Germany), G. Rodriguez (INAF - IAPS, Roma, Italy) G. Rowell (University of Ade- laide, Australia) P. Romano (INAF - Osservatorio di Brera, Italy), M. Roncadelli (INFN - Sezione di Pavia, Pavia, Italy), G. Romeo (INAF - Osservatorio Astrofisico di Catania, Italy), B. Rudak (CAMK PAN, Torun, Poland) F. Salesa Greus (Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland), F. G. Saturni (INAF - Osservatorio Astronomico di Roma, Italy), U. Sawangwit (National Astronomical CTA Consortium Page 2 of8 j Issue 0 j Rev. 1 Origin and role of relativistic cosmic particles 1. Cosmic Accelerators Research Institute of Thailand, Thailand), F. Schussler¨ (IRFU, CEA Paris-Saclay), O. Sergijenko (Taras Shevchenko National University of Kyiv, Ukraine), H. Sol (LUTH, Observatoire de Paris, CNRS, France), A. Stamerra (INAF, Osservatorio Astronomico di Roma, Italy), T. Stolarczyk (AIM, CEA, CNRS, Univer- site´ Paris-Saclay, Universite´ de Paris, France) G. Tagliaferri (INAF-Osservatorio Astronomico di Brera, Italy), F. Tavecchio (INAF-Osservatorio Astronomico di Brera, Italy), V. Testa (INAF - Osservatorio Astro- nomico di Roma, Italy), L. Tibaldo (IRAP,Universite´ de Toulouse, CNRS, UPS, CNES, Toulouse, France), A. Viana (IFSC - Universidade de Sao˜ Paulo, Brazil), S. Vercellone (INAF - Osservatorio di Brera, Italy), S. Ventura (University of Siena - INFN Pisa, Italy), J. Vink (Anton Pannekoek Institute/GRAPPA, Uni- versity of Amsterdam, Netherlands), S. Vorobiov (University of Nova Gorica, Slovenia), V. Vitale (INFN, Roma Tor Vergata), I. Sadeh (DESY-Zeuthen, Germany), P. Sharma (IJClab, IN2P3/CNRS, Universite´ Paris-Saclay, Universite´ de Paris, France) R. C. Shellard (Centro Brasileiro de Pesquisas F´ısicas, Brazil) T. Suomijarvi¨ (IJClab, IN2P3/CNRS, Universite´ Paris-Saclay, Universite´ de Paris, France) A. Wierzchol- ska (Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland) on beahlf of the CTA consortium. Introduction Relativistic particles play a major role in a wide range of astrophysical systems, from pulsars and super- nova remnants in our own Galaxy, to active galactic nuclei and clusters of galaxies. Within the interstellar medium of our Galaxy, these cosmic rays (CRs) are close to pressure equilibrium with interstellar gas and magnetic fields – yet the relationship between these three components, and the overall impact on ionization and chemical evolution of the interstellar medium, the star-formation process and the evolu- tion of galaxies, is very poorly understood. In the coming decade, ground-based observatories have the potential to provide high-angular resolution measurements of gamma-rays resulting from the interaction of CRs with matter and photon fields, allowing to detect over-densities of CR protons and nuclei. This is in addition to gamma-ray emission associated with the energetically sub-dominant electrons that also produce the non-thermal emission seen at radio and X-ray wavelengths. These observations will pro- vide insights into the mechanisms of CRs acceleration, transport, and feedback, thus making a major contribution to our deepening understanding of the processes by which galaxies and clusters of galaxies evolve. Below we introduce the main elements of this theme, beginning with the accelerators themselves, and then moving