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1. Gamma-rays and neutrinos from RX J1713–3946 in a lepto–hadronic scenario

Author

Stefano Gabici, P. Cristofari, Viviana Niro, Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Hadron, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Electron, GeV, gamma ray: energy spectrum, p: acceleration, 01 natural sciences, thermal, cosmic rays, 0103 physical sciences, TeV, stars: general, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Range (particle radiation), lepton hadron, 010308 nuclear & particles physics, nucleus, density: low, electron: cosmic radiation, Gamma ray, Compton scattering, Astronomy and Astrophysics, gamma-rays: general, Interstellar medium, gamma ray: emission, Compton scattering: inverse, Space and Planetary Science, High Energy Physics::Experiment, Neutrino, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The gamma-ray emission of RX J1713–3946, despite being extensively studied in the GeV and TeV domains, remains poorly understood. This is mostly because, in this range, two competing mechanisms can efficiently produce gamma-rays: the inverse Compton scattering of accelerated electrons, and interactions of accelerated protons with the nuclei of the interstellar medium (ISM). In addition to the acceleration of particles from the thermal pool, the re-acceleration of pre-existing cosmic rays is often overlooked, and has in fact also been taken into account. Especially, because of the distance to the SNR (∼1 kpc), and the low density in which the shock is currently expanding (∼10−2 cm−3), the re-acceleration of cosmic-ray electrons pre-existing in the ISM can account for a significant fraction of the observed gamma-ray emission, and contribute to the shaping of the spectrum in the GeV–TeV range. Remarkably, this emission of leptonic origin is found to be close to the level of the gamma-ray signal in the TeV range, provided that the spectrum of pre-exisiting cosmic-ray electrons is similar to that observed in the local ISM. The overall gamma-ray spectrum of RX J1713–3946 is naturally produced as the sum of leptonic emission from re-accelerated cosmic-ray electrons, and a subdominant hadronic emission from accelerated protons. We also argue that neutrino observations with next-generation detectors might lead to a detection even in the case of a lepto–hadronic origin of the gamma-ray emission.

Published
2021
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2. Constraining leptonic emission scenarios for the PeVatron candidate HESS J1702-420 with deep XMM-Newton observations

Author

L. Giunti, F. Acero, B. Khélifi, K. Kosack, A. Lemière, R. Terrier, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), ANR-18-IDEX-0001,Université de Paris,Université de Paris(2018), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, pulsars: general, FOS: Physical sciences, Astronomy and Astrophysics, gamma rays: general, radiation mechanisms: non-thermal, X-rays: general, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, methods: data analysis, acceleration of particles
Abstract

The unidentified TeV source HESS J1702-420 has recently been proposed as a new hadronic PeVatron candidate, based on the discovery of a small-scale emission sub-region with extremely hard gamma-ray spectrum up to 100 TeV (named HESS J1702-420A). Given the difficulty to discriminate between a hadronic or leptonic origin of the TeV emission, based on the H.E.S.S. measurement alone, we opted for a multi-wavelength approach. A deep X-ray observation was carried out using the XMM-Newton satellite, with the goal of probing a possible association with a hidden leptonic accelerator. No evidence of a clear counterpart for HESS J1702-420A was found in the X-ray data. After excluding an association with all nearby X-ray point sources, we derived strict upper limits on the diffuse X-ray emission and average magnetic field in the HESS J1702-420A region. We additionally report the serendipitous discovery of a new extended X-ray source, whose association with HESS J1702-420A is not obvious but cannot be ruled out either. A set of scripts dedicated to the multi-wavelength modeling of X-ray and gamma-ray data, based on Gammapy, Naima and Xspec, was developed in the context of this work and is made publicly available along with this paper., Accepted for publication in Astronomy & Astrophysics, 13 pages, 11 figures, 3 tables

Published
2022
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3. Low-energy cosmic rays: regulators of the dense interstellar medium

Author

Gabici, Stefano, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
Interstellar medium, Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Molecular clouds, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Cosmic rays, Astrophysics::Galaxy Astrophysics
Abstract

International audience; Low-energy cosmic rays (up to the GeV energy domain) play a crucial role in the physics and chemistry of the densest phase of the interstellar medium. Unlike interstellar ionising radiation, they can penetrate large column densities of gas, and reach molecular cloud cores. By maintaining there a small but not negligible gas ionisation fraction, they dictate the coupling between the plasma and the magnetic field, which in turn affects the dynamical evolution of clouds and impacts on the process of star and planet formation. The cosmic-ray ionisation of molecular hydrogen in interstellar clouds also drives the rich interstellar chemistry revealed by observations of spectral lines in a broad region of the electromagnetic spectrum, spanning from the submillimetre to the visual band. Some recent developments in various branches of astrophysics provide us with an unprecedented view on low-energy cosmic rays. Accurate measurements and constraints on the intensity of such particles are now available both for the very local interstellar medium and for distant interstellar clouds. The interpretation of these recent data is currently debated, and the emerging picture calls for a reassessment of the scenario invoked to describe the origin and/or the transport of low-energy cosmic rays in the Galaxy.

Published
2022
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4. The theory of cosmic ray scattering on pre-existing MHD modes meets data

Author

Stefano Gabici, Daniele Gaggero, Ottavio Fornieri, Silvio Sergio Cerri, Pedro De la Torre Luque, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
scattering [cosmic radiation], MHD, GeV, 01 natural sciences, galaxy: halo, High Energy Physics - Phenomenology (hep-ph), Diffusion (business), Anisotropy, 010303 astronomy & astrophysics, cosmic radiation: scattering, cosmic ray, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, energy: high, diffusion, secondary [cosmic radiation], suppression, cascade, halo [galaxy], High Energy Physics - Phenomenology, Cascade, cosmic radiation: galaxy, Physics::Space Physics, slope, high [energy], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, confinement [cosmic radiation], anisotropy, Galactic halo, 0103 physical sciences, waves, cosmic radiation: secondary, MHD waves -Magnetosonic modes -Cosmic-ray diffusion, fluctuation, 010308 nuclear & particles physics, Scattering, turbulence, cosmic radiation: confinement, Astronomy and Astrophysics, Physics - Plasma Physics, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], Computational physics, Plasma Physics (physics.plasm-ph), Space and Planetary Science, [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph], Scattering rate, hydrodynamics, ddc:520, galaxy [cosmic radiation], Magnetohydrodynamics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Monthly notices of the Royal Astronomical Society 502(4), 5821 - 5838 (2021). doi:10.1093/mnras/stab355, We present a comprehensive study about the phenomenological implications of the theory describing Galactic cosmic ray scattering on to magnetosonic and Alfv��nic fluctuations in the GeV���PeV domain. We compute a set of diffusion coefficients from first principles, for different values of the Alfv��nic Mach number and other relevant parameters associated with both the Galactic halo and the extended disc, taking into account the different damping mechanisms of turbulent fluctuations acting in these environments. We confirm that the scattering rate associated with Alfv��nic turbulence is highly suppressed if the anisotropy of the cascade is taken into account. On the other hand, we highlight that magnetosonic modes play a dominant role in Galactic confinement of cosmic rays up to PeV energies. We implement the diffusion coefficients in the numerical framework of the dragon code, and simulate the equilibrium spectrum of different primary and secondary cosmic ray species. We show that, for reasonable choices of the parameters under consideration, all primary and secondary fluxes at high energy (above a rigidity of |$\simeq 200 \, \mathrm{GV}$|���) are correctly reproduced within our framework, in both normalization and slope., Published by Oxford Univ. Press, Oxford

Published
2021
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5. Particle acceleration at colliding shock waves

Author

V. Tatischeff, T. Vieu, Stefano Gabici, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Shock wave, Physics, High energy, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Cosmic ray, shock waves, Collision, 01 natural sciences, Spectral line, Computational physics, Exponential function, Particle acceleration, cosmic rays, Space and Planetary Science, 0103 physical sciences, Cutoff, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, acceleration of particles
Abstract

We model the diffusive shock acceleration of particles in a system of two colliding shock waves and present a method to solve the time-dependent problem analytically in the test-particle approximation and high energy limit. In particular, we show that in this limit the problem can be analysed with the help of a self-similar solution. While a number of recent works predict hard ($E^{-1}$) spectra for the accelerated particles in the stationary limit, or the appearance of spectral breaks, we found instead that the spectrum of accelerated particles in a time-dependent collision follows quite closely the canonical $E^{-2}$ prediction of diffusive shock acceleration at a single shock, except at the highest energy, where a hardening appears, originating a bumpy feature just before the exponential cutoff. We also investigated the effect of the reacceleration of pre-existing cosmic rays by a system of two shocks, and found that under certain conditions spectral features can appear in the cutoff region. Finally, the mathematical methods presented here are very general and could be easily applied to a variety of astrophysical situations, including for instance standing shocks in accretion flows, diverging shocks, backward collisions of a slow shock by a faster shock, and wind-wind or shock-wind collisions., 11 pages, 8 figures

Published
2020
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6. Cosmic ray production in superbubbles

Author

T Vieu, S Gabici, V Tatischeff, S Ravikularaman, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, collective, FOS: Physical sciences, feedback, Astrophysics::Cosmology and Extragalactic Astrophysics, GeV, plasma: effect, cosmic rays, supernova, intermittency, acceleration: stochastic, energy: density, Astrophysics::Galaxy Astrophysics, acceleration of particles, cosmic radiation: production, energy: low, High Energy Astrophysical Phenomena (astro-ph.HE), energy: high, particle: energy, bubble, turbulence, cosmic radiation: confinement, Astronomy and Astrophysics, shock waves, cascade, star: massive, injection, Space and Planetary Science, gamma ray, cosmic radiation: galaxy, cluster: massive, nonlinear, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], signature
Abstract

We compute the production of cosmic rays in the dynamical superbubble produced by a cluster of massive stars. Stellar winds, supernova remnants and turbulence are found to accelerate particles so efficiently that the nonlinear feedback of the particles must be taken into account in order to ensure that the energy balance is not violated. High energy particles do not scatter efficiently on the turbulence and escape quickly after each supernova explosion, which makes both their intensity inside the bubble and injection in the interstellar medium intermittent. On the other hand, the stochastic acceleration of low energy particles hardens the spectra at GeV energies. Because cosmic rays damp the turbulence cascade, this hardening is less pronounced when nonlinearities are taken into account. Nevertheless, spectra with hard components extending up to 1 to 10 GeV and normalised to an energy density of 1 to 100 eV cm$^{-3}$ are found to be typical signatures of cosmic rays produced in superbubbles. Efficient shock reacceleration within compact clusters is further shown to produce hard, slightly concave spectra, while the presence of a magnetised shell is shown to enhance the confinement of cosmic rays in the bubble and therefore the collective plasma effects acting on them. We eventually estimate the overall contribution of superbubbles to the galactic cosmic ray content and show typical gamma-ray spectra expected from hadronic interactions in superbuble shells. In both cases, a qualitative agreement with observations is obtained., Comment: 20 pages, 14 figures

Published
2022
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7. Search for New Cosmic-Ray Acceleration Sites within the 4FGL Catalog Galactic Plane Sources

Author

Collaboration, Fermi-LAT, Abdollahi, S., Acero, F., Ackermann, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Berenji, B., Berretta, A., Bissaldi, E., Blandford, R. D., Bonino, R., Bruel, P., Buson, S., Cameron, R. A., Caputo, R., Caraveo, P. A., Castro, D., Chiaro, G., Cibrario, N., Ciprini, S., Coronado-Blázquez, J., Crnogorcevic, M., Cutini, S., D'Ammando, F., De Gaetano, S., Di Lalla, N., Dirirsa, F., Di Venere, L., Domínguez, A., Fegan, S. J., Fiori, A., Fleischhack, H., Franckowiak, A., Fukazawa, Y., Fusco, P., Gammaldi, V., Gargano, F., Gasparrini, D., Giacchino, F., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Green, D., Grenier, I. A., Grondin, M. -H., Guiriec, S., Gustafsson, M., Harding, A. K., Hays, E., Hewitt, J. W., Horan, D., Hou, X., Jóhannesson, G., Kayanoki, T., Kerr, M., Kuss, M., Larsson, S., Latronico, L., Lemoine-Goumard, M., Li, J., Longo, F., Loparco, F., Lubrano, P., Maldera, S., Malyshev, D., Manfreda, A., Martí-Devesa, G., Mazziotta, M. N., Mereu, I., Michelson, P. F., Mirabal, N., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Nuss, E., Omodei, N., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Pei, Z., Persic, M., Pesce-Rollins, M., Pillera, R., Poon, H., Porter, T. A., Principe, G., Rainò, S., Rando, R., Rani, B., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Reposeur, T., Sánchez-Conde, M., Parkinson, P. M. Saz, Scotton, L., Serini, D., Sgrò, C., Siskind, E. J., Spandre, G., Spinelli, P., Sueoka, K., Suson, D. J., Tajima, H., Tak, D., Thayer, J. B., Torres, D. F., Troja, E., Valverde, J., Wadiasingh, Z., Wood, K., Zaharijas, G., Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Deux Infinis Bordeaux (LP2I - Bordeaux), Université de Bordeaux (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Fermi-LAT, ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), Department of Energy (US), Centre National de la Recherche Scientifique (France), Agenzia Spaziale Italiana, Ministry of Education, Culture, Sports, Science and Technology (Japan), Swedish Research Council, Agence Nationale de la Recherche (France), and National Aeronautics and Space Administration (US)

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astronomi, astrofysik och kosmologi, Space and Planetary Science, Astronomy, Astrophysics and Cosmology, ddc:520, Physics::Accelerator Physics, Astrophysics - High Energy Astrophysical Phenomena, Nuclear Experiment, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics::Galaxy Astrophysics
Abstract

Abdollahi et al., Cosmic rays are mostly composed of protons accelerated to relativistic speeds. When those protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma-rays. This offers a compelling way to identify the acceleration sites of protons. A characteristic hadronic spectrum, with a low-energy break around 200 MeV, was detected in the gamma-ray spectra of four supernova remnants (SNRs), IC 443, W44, W49B, and W51C, with the Fermi Large Area Telescope. This detection provided direct evidence that cosmic-ray protons are (re-)accelerated in SNRs. Here, we present a comprehensive search for low-energy spectral breaks among 311 4FGL catalog sources located within 5° from the Galactic plane. Using 8 yr of data from the Fermi Large Area Telescope between 50 MeV and 1 GeV, we find and present the spectral characteristics of 56 sources with a spectral break confirmed by a thorough study of systematic uncertainty. Our population of sources includes 13 SNRs for which the proton–proton interaction is enhanced by the dense target material; the high-mass gamma-ray binary LS I+61 303; the colliding wind binary η Carinae; and the Cygnus star-forming region. This analysis better constrains the origin of the gamma-ray emission and enlarges our view to potential new cosmic-ray acceleration sites., The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Etudes Spatiales in France. Work at NRL is supported by NASA. M.L.G. acknowledges support from Agence Nationale de la Recherche (grant ANR- 17-CE31-0014).

Published
2022
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8. Characterization of the Gamma-ray Emission from the Kepler Supernova Remnant with Fermi-LAT

Author

F. Acero, M. Lemoine-Goumard, J. Ballet, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
supernovae: individual: Kepler, supernova remnants, cosmic rays, Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astronomy and Astrophysics, shock waves, Astrophysics::Galaxy Astrophysics, acceleration of particles
Abstract

The Kepler supernova remnant (SNR) had been the only historic SNR that lacked a detection at GeV and TeV energies, which probe particle acceleration. A recent analysis of Fermi-LAT data reported a likely GeV γ-ray candidate in the direction of the SNR. Using approximately the same data set but with an optimized analysis configuration, we confirm the γ-ray candidate to a solid >6σ detection and report a spectral index of 2.14 ± 0.12stat ± 0.15syst for an energy flux above 100 MeV of (3.1 ± 0.6stat ± 0.3syst) × 10−12 erg cm−2 s−1. The γ-ray excess is not significantly extended and is fully compatible with the radio, infrared, and X-ray spatial distribution of the SNR. We successfully characterized this multiwavelength emission with a model in which accelerated particles interact with the dense circumstellar material in the northwest portion of the SNR and radiate GeV γ rays through π° decay. The X-ray synchrotron and inverse-Compton emission mostly stem from the fast shocks in the southern regions with a magnetic field B ~ 100 μG or higher. Depending on the exact magnetic field amplitude, the TeV γ-ray emission could arise from either the south region (inverse-Compton dominated) or the interaction region (π° decay dominated).

Published
2022
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9. Giant cosmic ray halos around M31 and the Milky Way

Author

Felix Aharonian, Stefano Gabici, Viviana Niro, Sarah Recchia, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
010504 meteorology & atmospheric sciences, Andromeda Galaxy, Milky Way, Astrophysics::High Energy Astrophysical Phenomena, halo, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxies: halos, GeV, 01 natural sciences, neutrino: flux, particle: acceleration, accretion, cosmic rays, gas, 0103 physical sciences, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], cosmic radiation: propagation, Galactic Center, nucleus, neutrinos, Astronomy and Astrophysics, Accretion (astrophysics), Galaxy, gamma rays, gamma ray: emission, Space and Planetary Science, p: cosmic radiation, Intergalactic travel, Halo, galaxy, Neutrino, Neutrino astronomy, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Recently, a diffuse emission of 1-100 GeV $\gamma$-rays has been detected from the direction of Andromeda. The emission is centered on the galaxy, and extends for $\sim 100-200$ kpc away from its center. Explaining the extended $\gamma-$ray emission within the framework of standard scenarios for the escape of cosmic rays injected in the galactic disk or in the galactic center is problematic. In this paper, we argue that a cosmic ray origin (either leptonic or hadronic) of the $\gamma$-ray emission is possible in the framework of non standard cosmic ray propagation scenarios or in the case of particle acceleration taking place in the galaxy's halo. It would imply the existence of a giant cosmic ray halo surrounding M31, possibly powered by the galaxy nuclear activity, or by accretion of intergalactic gas. Remarkably, if cosmic ray halos, as the one observed around M31, are a common feature of galaxies, including our own, the interactions between cosmic ray protons and the Milky Way circumgalactic gas could also explain the isotropic diffuse flux of neutrinos observed by Icecube., Comment: Submitted to ApJ, 13 pages, 3 figures

Published
2021
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10. The Origin of Galactic Cosmic Rays as Revealed by their Composition

Author

Jean Duprat, John C. Raymond, Vincent Tatischeff, Sarah Recchia, Stefano Gabici, Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de recherche pour le développement [IRD] : UR206-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
stars: abundances, Milky Way, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, ISM: abundances, Luminosity, cosmic rays, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Cosmic dust, High Energy Astrophysical Phenomena (astro-ph.HE), supernova remnants, [PHYS]Physics [physics], Physics, 010308 nuclear & particles physics, Molecular cloud, Astronomy and Astrophysics, Plasma, Interstellar medium, Supernova, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract

Galactic cosmic-rays (GCRs) are thought to be accelerated in strong shocks induced by massive star winds and supernova explosions sweeping across the interstellar medium. But the phase of the interstellar medium from which the CRs are extracted has remained elusive until now. Here, we study in detail the GCR source composition deduced from recent measurements by the AMS-02, Voyager 1 and SuperTIGER experiments to obtain information on the composition, ionisation state and dust content of the GCR source reservoirs. We show that the volatile elements of the CR material are mainly accelerated from a plasma of temperature higher than $\sim 2$ MK, which is typical of the hot medium found in galactic superbubbles energised by the activity of massive star winds and supernova explosions. Another GCR component, which is responsible for the overabundance of $^{22}$Ne, most likely arises from acceleration of massive star winds in their termination shocks. From the CR-related $\gamma$-ray luminosity of the Milky Way, we estimate that the ion acceleration efficiency in both supernova shocks and wind termination shocks is of the order of $10^{-5}$. The GCR source composition also shows evidence for a preferential acceleration of refractory elements contained in interstellar dust. We suggest that the GCR refractories are also produced in superbubbles, from shock acceleration and subsequent sputtering of dust grains continuously incorporated into the hot plasma through thermal evaporation of embedded molecular clouds. Our model explains well the measured abundances of all primary and mostly primary CRs from H to Zr, including the overabundance of $^{22}$Ne., Comment: 24 pages, 18 figures, submitted to MNRAS. Version 2: as accepted for publication

Published
2021
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11. Cosmic ray driven galactic winds

Author

Sarah Recchia, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
Physics, ISM kinematics and dynamics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, ISM cosmic rays, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Galaxy, galaxies evolution, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Physics::Space Physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Phenomenology (particle physics), Mathematical Physics, Astrophysics::Galaxy Astrophysics, Physics::Atmospheric and Oceanic Physics
Abstract

International audience; Galactic winds constitute a primary feedback process in the ecology and evolution of galaxies. They are ubiquitously observed and exhibit a rich phenomenology, whose origin is actively investigated both theoretically and observationally. Cosmic rays have been widely recognized as a possible driving agent of galactic winds, especially in Milky–Way like galaxies. The formation of cosmic ray-driven winds is intimately connected with the microphysics of the cosmic ray transport in galaxies, making it an intrinsically non-linear and multiscale phenomenon. In this complex interplay, the cosmic ray distribution affects the wind launching and, in turns, is shaped by the presence of winds. In this review, we summarize the present knowledge of the physics of cosmic rays involved in the wind formation and of the wind hydrodynamics. We also discuss the theoretical difficulties connected with the study of cosmic ray-driven winds and possible future improvements and directions.

Published
2021
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12. Multiwavelength constraints on the unidentified Galactic TeV sources HESS J1427$-$608, HESS J1458$-$608, and new VHE $\gamma$-ray source candidates

Author

Marianne Lemoine-Goumard, G. Vasileiadis, Matthieu Renaud, J. Devin, Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Population, ISM: individual objects: HESS J1458-608, magnetic field, Context (language use), Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, power spectrum, GeV, 01 natural sciences, Pulsar wind nebula, GLAST, thermal, X-ray, gamma rays: ISM, cosmic rays, Pulsar, HESS, synchrotron, supernova, 0103 physical sciences, ISM: individual objects: HESS J1427-608, TeV, education, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ISM: supernova remnants, pulsar, 0105 earth and related environmental sciences, Physics, education.field_of_study, Spectral index, Gamma ray, Astronomy and Astrophysics, Galactic plane, radio continuum: ISM, gamma ray: VHE, Space and Planetary Science, spectral, galaxy, data management, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Aims. Among the γ-ray sources discovered at high and very-high energies, a large fraction still lack a clear identification. In particular, the H.E.S.S. Galactic Plane Survey (HGPS) revealed 78 TeV sources among which 47 are not clearly associated with a known object. Multiwavelength data can help identify the origin of the very-high energy γ-ray emission, although some bright TeV sources have been detected without clear counterparts. We present a multiwavelength approach to constrain the origin of the emission from unidentified HGPS sources. Methods. We present a generic pipeline that explores a large database of multiwavelength archival data toward any region in the Galactic plane. Along with a visual inspection of the retrieved multiwavelength observations to search for faint and uncataloged counterparts, we derive a radio spectral index that helps disentangle thermal from nonthermal emission and a mean magnetic field through X-ray and TeV data in case of a leptonic scenario. We also search for a spectral connection between the GeV and the TeV regimes with the Fermi-LAT cataloged sources that may be associated with the unidentified HGPS source. We complete the association procedure with catalogs of known objects (supernova remnants, pulsar wind nebulae, H II regions, etc.) and with the source catalogs from instruments whose data are retrieved. Results. The method is applied on two unidentified sources, namely HESS J1427−608 and HESS J1458−608, for which the multiwavelength constraints favor the pulsar wind nebula (PWN) scenario. We model their broadband nonthermal spectra in a leptonic scenario with a magnetic field B ≲ 10 μG, which is consistent with that obtained from ancient PWNe. We place both sources within the context of the TeV PWN population to estimate the spin-down power and the characteristic age of the putative pulsar. We also shed light on two possibly significant γ-ray excesses in the HGPS: the first is located in the south of the unidentified source HESS J1632−478 and the second is spatially coincident with the synchrotron-emitting supernova remnant G28.6−0.1. The multiwavelength counterparts found toward both γ-ray excesses make these promising candidates for being new very-high energy γ-ray sources.

Published
2021
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13. Constraining the Origin of the Puzzling Source HESS J1640−465 and the PeVatron Candidate HESS J1641−463 Using Fermi-Large Area Telescope Observations

Author

M.-H. Grondin, Fabio Acero, C. J. Clark, M. Lemoine-Goumard, J. D. Gelfand, J. Devin, Arnaud Mares, Dave Green, S. Gabici, Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Mares, A [0000-0003-3345-7800], Lemoine-Goumard, M [0000-0002-4462-3686], Clark, CJ [0000-0003-4355-3572], Gelfand, JD [0000-0003-4679-1058], Green, DA [0000-0003-3189-9998], Grondin, MH [0000-0002-8383-251X], Apollo - University of Cambridge Repository, Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, GeV, power spectrum, 01 natural sciences, GLAST, VHE, law.invention, Telescope, particle: acceleration, Pulsar, law, HESS, 0103 physical sciences, supernova, cloud, flux: upper limit, 010303 astronomy & astrophysics, X-ray: flux, Astrophysics::Galaxy Astrophysics, pulsar, Physics, astro-ph.HE, cosmic radiation: spectrum, 010308 nuclear & particles physics, Astronomy, Astronomy and Astrophysics, Gamma-ray astronomy, 13. Climate action, Space and Planetary Science, gamma ray, curvature, spectral, High Energy Physics::Experiment, galaxy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Fermi Gamma-ray Space Telescope
Abstract

There are only a few very-high-energy sources in our Galaxy that might accelerate particles up to the knee of the cosmic-ray spectrum. To understand the mechanisms of particle acceleration in these PeVatron candidates, Fermi-Large Area Telescope (LAT) and High-Energy Stereoscopic System (H.E.S.S.) observations are essential to characterize their γ-ray emission. HESS J1640–465 and the PeVatron candidate HESS J1641–463 are two neighboring (0.25°) γ-ray sources, spatially coincident with the radio supernova remnants (SNRs) G338.3–0.0 and G338.5+0.1. Detected both by H.E.S.S. and the Fermi-LAT, we present here a morphological and spectral analysis of these two sources using 8 yr of Fermi-LAT data between 200 MeV and 1 TeV with multiwavelength observations to assess their nature. The morphology of HESS J1640–465 is described by a 2D Gaussian (σ = 0.053° ± 0.011°stat ± 0.03°syst) and its spectrum is modeled by a power law with a spectral index Γ = 1.8 ± 0.1stat ± 0.2syst. HESS J1641–463 is detected as a point-like source and its GeV emission is described by a logarithmic-parabola spectrum with α = 2.7 ± 0.1stat ± 0.2syst and significant curvature of β = 0.11 ± 0.03stat ± 0.05syst. Radio and X-ray flux upper limits were derived. We investigated scenarios to explain their emission, namely, the emission from accelerated particles within the SNRs spatially coincident with each source, molecular clouds illuminated by cosmic rays from the close-by SNRs, and a pulsar/pulsar wind nebula origin. Our new Fermi-LAT results and the radio and flux X-ray upper limits pose severe constraints on some of these models.

Published
2021
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14. Spectral signatures of PeVatrons

Author

Stefano Gabici, Silvia Celli, Felix Aharonian, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
p p: scattering, 010504 meteorology & atmospheric sciences, accelerator, Astrophysics::High Energy Astrophysical Phenomena, Synchrotron radiation, FOS: Physical sciences, magnetic field, Electron, Radiation, 01 natural sciences, 7. Clean energy, UHE, Secondary electrons, law.invention, Nuclear physics, neutrino, law, 0103 physical sciences, Spectral energy distribution, Gamma-rays, Particle astrophysics, High-energy cosmic radiation, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), cosmic radiation: particle source, Range (particle radiation), synchrotron radiation: energy spectrum, Gamma ray, Astronomy and Astrophysics, Particle accelerator, electron: secondary, stability, Space and Planetary Science, gamma ray, p: primary, spectral, Physics::Accelerator Physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, signature
Abstract

We analyze the energy distributions of final (stable) products - gamma rays, neutrinos, and electrons - produced in inelastic proton-proton collisions in the PeV energy regime. We also calculate the energy spectrum of synchrotron radiation from secondary electrons, assuming that these are promptly cooled in the surrounding magnetic field. We show that the synchrotron radiation has an energy distribution much shallower than that of primary protons, and hence we suggest to take advantage of such a feature in the spectral analysis of the highest energy (cut-off) emission region from particle accelerators. For a broad range of energy distributions in the parent protons, we propose simple analytical presentations for the spectra of secondaries in the cut-off region. These results can be used in the interpretation of high-energy radiation from PeVatrons - cosmic-ray factories accelerating protons to energies up to 1 PeV., 14 pages, 6 figures. Accepted by ApJ

Published
2020
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15. Constraining the cosmic ray spectrum in the vicinity of the supernova remnant W28: from sub-GeV to multi-TeV energies

Author

Regis Terrier, V. H. M. Phan, Julian Krause, Mélissa D. Menu, Stefano Gabici, Giovanni Morlino, Jacco Vink, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), GRAPPA & Anton Pannekoek Institute for Astronomy, University of Amsterdam [Amsterdam] (UvA), Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Observatory of Paris (Action Fédératrice CTA)., ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), European Project: 665850,H2020,H2020-MSCA-COFUND-2014,INSPIRE(2015), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), High Energy Astrophys. & Astropart. Phys (API, FNWI), Gravitation and Astroparticle Physics Amsterdam, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Université Paris-Sud - Paris 11 (UP11)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-École polytechnique (X)-Sorbonne Universités-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, ISM: clouds, cosmic rays, Ionization, 0103 physical sciences, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ISM: supernova remnants, High Energy Astrophysical Phenomena (astro-ph.HE), Astroparticle physics, Physics, 010308 nuclear & particles physics, Molecular cloud, Gamma ray, Astronomy and Astrophysics, Supernova, 13. Climate action, Space and Planetary Science, astroparticle physics, ISM: individual objects: W28, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Radio wave
Abstract

Supernova remnants interacting with molecular clouds are ideal laboratories to study the acceleration of particles at shock waves and their transport and interactions in the surrounding interstellar medium. In this paper, we focus on the supernova remnant W28, which over the years has been observed in all energy domains from radio waves to very-high-energy gamma rays. The bright gamma-ray emission detected from molecular clouds located in its vicinity revealed the presence of accelerated GeV and TeV particles in the region. An enhanced ionization rate has also been measured by means of millimetre observations, but such observations alone cannot tell us whether the enhancement is due to low energy (MeV) cosmic rays (either protons or electrons) or the X-ray photons emitted by the shocked gas. The goal of this study is to determine the origin of the enhanced ionization rate and to infer from multiwavelength observations the spectrum of cosmic rays accelerated at the supernova remnant shock in the unprecedented range spanning from MeV to multi-TeV particle energies. We developed a model to describe the transport of X-ray photons into the molecular cloud, and we fitted the radio, millimeter, and gamma-ray data to derive the spectrum of the radiating particles. The contribution from X-ray photons to the enhanced ionization rate is negligible, and therefore the ionization must be due to cosmic rays. Even though we cannot exclude a contribution to the ionization rate coming from cosmic ray electrons, we show that a scenario where cosmic ray protons explain both the gamma-ray flux and the enhanced ionization rate provides the most natural fit to multiwavelength data. This strongly suggests that the intensity of CR protons is enhanced in the region for particle energies in a very broad range covering almost 6 orders of magnitude: from $\lesssim 100$ MeV up to several tens of TeV., 8 pages, 6 figures, submitted

Published
2020
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16. High-energy gamma-ray study of the dynamically young SNR G150.3+4.5

Author

J. Devin, John W. Hewitt, Marie-Hélène Grondin, Daniel Castro, Jean Ballet, Jamie Cohen, Marianne Lemoine-Goumard, Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Météo-France Direction Interrégionale Sud-Est (DIRSE), Météo-France, ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), and Météo France

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, magnetic field, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, power spectrum, 01 natural sciences, Radio spectrum, GLAST, thermal, particle: acceleration, gamma rays: ISM, cosmic rays, Angular diameter, 0103 physical sciences, ROSAT, supernova, X-ray: emission, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ISM: supernova remnants, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Spectral index, radio wave, density, 010308 nuclear & particles physics, photon, Astronomy and Astrophysics, Particle acceleration, Space and Planetary Science, gamma ray, spectral, galaxy, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Fermi Gamma-ray Space Telescope
Abstract

Aims. The supernova remnant (SNR) G150.3+4.5 was recently discovered in the radio band; it exhibits a shell-like morphology with an angular size of ~ 3°, suggesting either an old or a nearby SNR. Extended γ-ray emission spatially coincident with the SNR was reported in the Fermi Galactic Extended Source Catalog, with a power-law spectral index of Γ = 1.91 ± 0.09. Studying particle acceleration in SNRs through their γ-ray emission is of primary concern to assess the nature of accelerated particles and the maximum energy they can reach. Methods. Using more than ten years of Fermi-LAT data, we investigate the morphological and spectral properties of the SNR G150.3+4.5 from 300 MeV to 3 TeV. We use the latest releases of the Fermi-LAT catalog, the instrument response functions and the Galactic and isotropic diffuse emissions. We use ROSAT all-sky survey data to assess any thermal and nonthermal X-ray emission, and we derive minimum and maximum distance to G150.3+4.5. Results. We describe the γ-ray emission of G150.3+4.5 by an extended component which is found to be spatially coincident with the radio SNR. The spectrum is hard and the detection of photons up to hundreds of GeV points towards an emission from a dynamically young SNR. The lack of X-ray emission gives a tight constraint on the ambient density n0 ≤ 3.6 × 10−3 cm−3. Since G150.3+4.5 is not reported as a historical SNR, we impose a lower limit on its age of t = 1 kyr. We estimate its distance to be between 0.7 and 4.5 kpc. We find that G150.3+4.5 is spectrally similar to other dynamically young and shell-type SNRs, such as RX J1713.7−3946 or Vela Junior. The broadband nonthermal emission is explained with a leptonic scenario, implying a downstream magnetic field of B = 5 μG and acceleration of particles up to few TeV energies.

Published
2020
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17. Neutrinos from the gamma-ray source eHWC J1825-134: predictions for Km$^3$ detectors

Author

D.V. Semikoz, Viviana Niro, Andrii Neronov, Stefano Gabici, L. Fusco, AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)

Subjects
media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, High-energy neutrinos, FOS: Physical sciences, Astrophysics, power spectrum, 7. Clean energy, 01 natural sciences, High Energy Physics - Phenomenology (hep-ph), Observatory, High-energy cosmic-ray physics and astrophysics, 0103 physical sciences, gamma ray: flux, 010303 astronomy & astrophysics, KM3NeT, media_common, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Spectral index, 010308 nuclear & particles physics, Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, suppression, observatory, High Energy Physics - Phenomenology, neutrino: detector, Neutrino detector, 13. Climate action, Sky, Neutrino astronomy, [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph], Neutrino, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], HAWC
Abstract

The eHWC J1825-134 source is located in the southern sky and has been recently detected by the HAWC observatory. It presents an hard spectral index and its gamma-ray flux extends up to energies close to 100 TeV without significant suppression. Amongst the HAWC sources, it is the most luminous in the multi-TeV domain and therefore is one of the first that should be searched for with a neutrino telescope in the northern hemisphere. Using an updated effective area for the forthcoming KM3NeT detector, we study the possibility to detect this source within ten years of its running time. We conclude that about a 4 to 5 sigma detection has to be expected after ten years of observations, depending on the details of the considered scenario., Comment: 10 pages, 4 figures, 2 tables. Typos corrected, updated references, acknowledgments and plots, conclusions unchanged

Published
2019
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18. An X-ray chimney extending hundreds of parsecs above and below the Galactic Centre

Author

Andrea Goldwurm, Mark Morris, E. M. Churazov, K. Nandra, Frank Haberl, Regis Terrier, Gabriele Ponti, F. Hofmann, Maïca Clavel, AstroParticule et Cosmologie (APC (UMR_7164)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Multidisciplinary, Plane (geometry), Milky Way, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galactic plane, 01 natural sciences, Galaxy, Relativistic particle, 0103 physical sciences, ROSAT, Chimney, 010306 general physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Fermi Gamma-ray Space Telescope
Abstract

Evidence has mounted in recent decades that outflows of matter and energy from the central few parsecs of our Galaxy have shaped the observed structure of the Milky Way on a variety of larger scales1. On scales of 15 parsecs, the Galactic Centre has bipolar lobes that can be seen in both the X-ray and radio parts of the spectrum2,3, indicating broadly collimated outflows from the centre, directed perpendicular to the Galactic plane. On larger scales, approaching the size of the Galaxy itself, γ-ray observations have revealed the so-called `Fermi bubble' features4, implying that our Galactic Centre has had a period of active energy release leading to the production of relativistic particles that now populate huge cavities on both sides of the Galactic plane. The X-ray maps from the ROSAT all-sky survey show that the edges of these cavities close to the Galactic plane are bright in X-rays4-6. At intermediate scales (about 150 parsecs), radio astronomers have observed the Galactic Centre lobe, an apparent bubble of emission seen only at positive Galactic latitudes7,8, but again indicative of energy injection from near the Galactic Centre. Here we report prominent X-ray structures on these intermediate scales (hundreds of parsecs) above and below the plane, which appear to connect the Galactic Centre region to the Fermi bubbles. We propose that these structures, which we term the Galactic Centre `chimneys', constitute exhaust channels through which energy and mass, injected by a quasi-continuous train of episodic events at the Galactic Centre, are transported from the central few parsecs to the base of the Fermi bubbles4

Published
2019
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19. Exploring particle escape in supernova remnants through gamma rays

Author

Stefano Gabici, Silvia Celli, Felix Aharonian, Giovanni Morlino, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), ITA, FRA, DEU, Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), Gran Sasso Science Institute (GSSI), Istituto Nazionale di Fisica Nucleare (INFN), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Max-Planck-Institut für Kernphysik (MPIK), Max-Planck-Gesellschaft, ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics, 01 natural sciences, Power law, Acceleration, cosmic rays, 0103 physical sciences, Diffusion (business), Supernova remnant, 010303 astronomy & astrophysics, Cherenkov radiation, acceleration of particle, Astrophysics::Galaxy Astrophysics, acceleration of particles, ISM: supernova remnants, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Astronomy and Astrophysics, shock waves, Galaxy, Supernova, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The escape process of particles accelerated at supernova remnant (SNR) shocks is one of the poorly understood aspects of the shock acceleration theory. Here we adopt a phenomenological approach to study the particle escape and its impact on the gamma-ray spectrum resulting from hadronic collisions both inside and outside of a middle-aged SNR. Under the assumption that in the spatial region immediately outside of the remnant the diffusion coefficient is suppressed with respect to the average Galactic one, we show that a significant fraction of particles are still located inside the SNR long time after their nominal release from the acceleration region. This fact results into a gamma-ray spectrum that resembles a broken power law, similar to those observed in several middle-aged SNRs. Above the break, the spectral steepening is determined by the diffusion coefficient outside of the SNR and by the time dependence of maximum energy. Consequently, the comparison between the model prediction and actual data will contribute to determining these two quantities, the former being particularly relevant within the predictions of the gamma-ray emission from the halo of escaping particles around SNRs which could be detected with future Cherenkov telescope facilities. We also calculate the spectrum of run-away particles injected into the Galaxy by an individual remnant. Assuming that the acceleration stops before the SNR enters the snowplow phase, we show that the released spectrum can be a featureless power law only if the accelerated spectrum has a slope alpha > 4., 18 pages, 10 figures, accepted for publication in MNRAS

Published
2019
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20. The origin of Galactic cosmic rays: challenges to the standard paradigm

Author

Carmelo Evoli, Stefano Gabici, Daniele Gaggero, Paolo Lipari, Philipp Mertsch, Andrew W. Strong, Elena Orlando, Andrea Vittino, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
Particle propagation, particle acceleration, 95.85.Ry, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics, 01 natural sciences, Acceleration, cosmic rays, 96.50.S, 0103 physical sciences, the Galaxy, 96.50.Tf, 010306 general physics, 010303 astronomy & astrophysics, Mathematical Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Gamma ray, Astronomy and Astrophysics, acceleration, Galaxy, Particle acceleration, gamma rays, Space and Planetary Science, cosmic radiation: galaxy, particle propagation, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 13.85.Tp
Abstract

A critical review of the standard paradigm for the origin of Galactic cosmic rays is presented. Recent measurements of local and far-away cosmic rays reveal unexpected behaviours, which challenge the commonly accepted scenario. These recent findings are discussed, together with long-standing open issues. Despite the progress made thanks to ever-improving observational techniques and theoretical investigations, at present our understanding of the origin and of the behaviour of cosmic rays remains incomplete. We believe it is still unclear whether a modification of the standard paradigm, or rather a radical change of the paradigm itself is needed in order to interpret all the available data on cosmic rays within a self-consistent scenario., Review based on a series of discussions that took place at the "The High-Energy Universe: Gamma-Ray, Neutrino, and Cosmic-ray Astronomy" MIAPP workshop in 2018

Published
2019
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21. Can a cosmic ray carrot explain the ionization level in diffuse molecular clouds?

Author

Stefano Gabici, V. H. M. Phan, S. Recchia, Sayan Biswas, AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017)

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Range (particle radiation), 010308 nuclear & particles physics, Molecular cloud, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Cosmic ray, Fermi acceleration, Astrophysics, 01 natural sciences, ISM: clouds, Galaxy, Magnetic field, Orders of magnitude (time), cosmic rays, Space and Planetary Science, Ionization, 0103 physical sciences, ISM: magnetic fields, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics
Abstract

International audience; Low-energy cosmic rays are the major ionization agents of molecular clouds. However, it has been shown that, if the cosmic ray spectrum measured by Voyager 1 is representative of the whole Galaxy, the predicted ionization rate in diffuse clouds fails to reproduce data by 1–2 orders of magnitude, implying that an additional source of ionization must exist. One of the solutions proposed to explain this discrepancy is based on the existence of an unknown low-energy (in the range 1 keV–1 MeV, not probed by Voyager) cosmic ray component, called carrot when first hypothesized by Reeves and collaborators in the seventies. Here we investigate the energetic required by such scenario. We show that the power needed to maintain such low-energy component is comparable of even larger than that needed to explain the entire observed cosmic ray spectrum. Moreover, if the interstellar turbulent magnetic field has to sustain a carrot, through second-order Fermi acceleration, the required turbulence level would be definitely too large compared to the one expected at the scale resonant with such low-energy particles. Our study basically rules out all the plausible sources of a cosmic ray carrot, thus making such hidden component unlikely to be an appealing and viable source of ionization in molecular clouds.

Published
2019
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22. Non-linear diffusion of cosmic rays escaping from supernova remnants - II. Hot ionized media

Author

Loann Brahimi, S. Recchia, Lara Nava, Vladimir Ptuskin, Alexandre Marcowith, Stefano Gabici, ITA, FRA, RUS, AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), and Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], 010308 nuclear & particles physics, Turbulence, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], FOS: Physical sciences, Astronomy and Astrophysics, Cosmic ray, 01 natural sciences, Galaxy, Computational physics, Interstellar medium, Supernova, Space and Planetary Science, Ionization, 0103 physical sciences, Diffusion (business), Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Excitation
Abstract

We study the problem of the escape and transport of Cosmic-Rays (CR) from a source embedded in a fully ionised, hot phase of the interstellar medium (HIM). In particular, we model the CR escape and their propagation in the source vicinity taking into account excitation of Alfv\'enic turbulence by CR streaming and mechanisms damping the self-excited turbulence itself. Our estimates of escape radii and times result in large values (100 pc, $2\times10^5$ yr) for particle energies $\lesssim20$ GeV and smaller values for particles with increasing energies (35 pc and 14 kyr at 1 TeV). These escape times and radii, when used as initial conditions for the CR propagation outside the source, result in relevant suppression of the diffusion coefficient (by a factor 5-10) on time-scales comparable with their (energy dependent) escape time-scale. The damping mechanisms are fast enough that even on shorter time scales the Alfv\'enic turbulence is efficiently damped, and the ratio between random and ordered component of the magnetic field is $\delta B/B_0\ll 1$, justifying the use of quasi-linear theory. In spite of the suppressed diffusion coefficient, and then the increased residence time in the vicinity (, Comment: Published in MNRAS

Published
2019
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23. Supernova remnants in clumpy media: particle propagation and gamma-ray emission

Author

Felix Aharonian, Silvia Celli, Stefano Gabici, Giovanni Morlino, Gran Sasso Science Institute (GSSI), Istituto Nazionale di Fisica Nucleare (INFN), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Kernphysik (MPIK), Max-Planck-Gesellschaft, Dublin Institute for Advanced Studies (DIAS), ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), ITA, FRA, DEU, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), AstroParticule et Cosmologie ( APC - UMR 7164 ), and Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA )

Subjects
Shock wave, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ISM: supernova remnants, acceleration of particles, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Gamma ray, Astronomy and Astrophysics, Plasma, shock waves, radiation mechanisms: non-thermal, gamma-rays: general, Cherenkov Telescope Array, Particle acceleration, Supernova, Wavelength, Space and Planetary Science, instabilities, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Observations from the radio to the gamma-ray wavelengths indicate that supernova remnant (SNR) shocks are sites of effective particle acceleration. It has been proposed that the presence of dense clumps in the environment where supernovae explode might have a strong impact in shaping the hadronic gamma-ray spectrum. Here we present a detailed numerical study about the penetration of relativistic protons into clumps which are engulfed by a SNR shock, taking into account the magneto-hydrodynamical properties of the background plasma. We show that the spectrum of protons inside clumps is much harder than that in the diffuse inter-clump medium and we discuss the implications for the formation of the spectrum of hadronic gamma rays, which does not reflect anymore the acceleration spectrum of protons, resulting substantially modified inside the clumps due to propagation effects. For the Galactic SNR RX J1713.7-3946, we show that a hadronic scenario including dense clumps inside the remnant shell is able to reproduce the broadband gamma-ray spectrum from GeV to TeV energies. Moreover, we argue that small clumps crossed by the shock could provide a natural explanation to the non-thermal X-ray variability observed in some hot spots of RX J1713.7-3946. Finally we discuss the detectability of gamma-ray emission from clumps with the upcoming Cherenkov Telescope Array and the possible detection of the clumps themselves through molecular lines., Comment: 15 pages, 10 figures, accepted for publication in MNRAS

Published
2019
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24. Contribution of the Galactic center to the local cosmic-ray flux

Author

Etienne Parizot, Etienne Jaupart, Denis Allard, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon), AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), École normale supérieure de Lyon (ENS de Lyon), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Cosmic ray, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, methods: analytical, cosmic rays, 0103 physical sciences, Disc, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Galaxy: center, 010308 nuclear & particles physics, diffusion, Astronomy and Astrophysics, Galaxy, Particle acceleration, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Halo, Astrophysics - High Energy Astrophysical Phenomena, ISM: bubbles, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Phenomenology (particle physics)
Abstract

Context. Recent observations of unexpected structures in the Galactic Cosmic Ray (GCR) spectrum and composition, as well as growing evidence for episodes of intense dynamical activity in the inner regions of the Galaxy, call for an evaluation of the high-energy particle acceleration associated with such activity and its potential impact on the global GCR phenomenology. Aims. We investigate whether particles accelerated during high-power episodes around the Galactic center can account for a significant fraction of the observed GCRs, or conversely what constraints can be derived regarding their Galactic transport if their contributions are negligible. Methods. We address these questions by studying the contribution of a continuous source of energetic particles at the Galactic center to the local GCRs. Particle transport in the Galaxy is described with a two-zone analytical model. We solve for the contribution of a Galactic Center Cosmic-Ray (GCCR) source using Green functions and Bessel expansion, and discuss the required injection power for these GCCRs to influence the global GCR phenomenology at Earth. Results. We find that, with standard parameters for particle propagation in the galactic disk and halo, the GCCRs can make a significant or even dominant contribution to the total CR flux observed at Earth. Depending on the parameters, such a source can account for both the observed proton flux and B-to-C ratio (in the case of a Kraichnan-like scaling of the diffusion coefficient), or potentially produce spectral and composition features. Conclusions. Our results show that the contribution of GCCRs cannot be neglected a priori, and that they can influence the global GCR phenomenology significantly, thereby calling for a reassessement of the standard inferences from a scenario where GCRs are entirely dominated by a single type of sources distributed throughout the Galactic disk., Comment: 10 pages, 13 figures, 1 table, accepted for publication in Astronomy and Astrophysics

Published
2018
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25. On the search for Galactic supernova remnant PeVatrons with current TeV instruments

Author

Stefano Gabici, P. Cristofari, Regis Terrier, T. B. Humensky, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), ANR-17-CE31-0014,PECORA,Rayons Cosmiques au PeV(2017), AstroParticule et Cosmologie ( APC - UMR 7164 ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, cosmic rays, 0103 physical sciences, supernova, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ISM: supernova remnants, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), lifetime, 010308 nuclear & particles physics, Gamma ray, Astronomy, Astronomy and Astrophysics, Supernova, Space and Planetary Science, gamma ray, cosmic radiation: galaxy, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The supernova remnant hypothesis for the origin of Galactic cosmic rays has passed several tests, but the firm identification of a supernova remnant pevatron, considered to be a decisive step to prove the hypothesis, is still missing. While a lot of hope has been placed in next-generation instruments operating in the multi-TeV range, it is possible that current gamma-ray instruments, operating in the TeV range, could pinpoint these objects or, most likely, identify a number of promising targets for instruments of next generation. Starting from the assumption that supernova remnants are indeed the sources of Galactic cosmic rays, and therefore must be pevatrons for some fraction of their lifetime, we investigate the ability of current instruments to detect such objects, or to identify the most promising candidates., Comment: 8 pages, 8 figures

Published
2018
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