A5054490106- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Neutrino Physics Research
- Solar and Space Plasma Dynamics
- Gamma-ray bursts and supernovae
- Particle physics theoretical and experimental studies
- Astrophysics and Star Formation Studies
- Particle Detector Development and Performance
- Radio Astronomy Observations and Technology
- High-Energy Particle Collisions Research
- Stellar, planetary, and galactic studies
- Atmospheric Ozone and Climate
- Galaxies: Formation, Evolution, Phenomena
- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Quantum Chromodynamics and Particle Interactions
- Ionosphere and magnetosphere dynamics
- Atomic and Subatomic Physics Research
- Astronomical Observations and Instrumentation
- Radiation Therapy and Dosimetry
- Spectroscopy and Laser Applications
- Particle Accelerators and Free-Electron Lasers
- History and Developments in Astronomy
- Photocathodes and Microchannel Plates
RWTH Aachen University
2017-2024
Max Planck Institute for Nuclear Physics
2023
FH Aachen
2022
Laboratoire AstroParticule et Cosmologie
2021
Université Paris Cité
2021
Centre National de la Recherche Scientifique
2021
University of Turin
2021
University of Oxford
2008-2021
Kavli Institute for Particle Astrophysics and Cosmology
2013-2019
Gran Sasso Science Institute
2019
We discuss recent observations of high energy cosmic ray positrons and electrons in the context hadronic interactions supernova remnants (SNRs), suspected accelerators galactic rays. Diffusive shock acceleration can harden spectrum secondary relative to that primary protons thus explain rise positron fraction observed by PAMELA above 10 GeV. normalize interaction rate holding pion decay be responsible for gamma rays detected HESS from some SNRs. By simulating spatial temporal distribution...
We revisit the model proposed earlier to account for observed increase in positron fraction cosmic rays with increasing energy, light of new data from Alpha Magnetic Spectrometer (AMS-02) experiment. The accounts production and acceleration secondary electrons positrons nearby supernova remnants which results an additional, harder component that becomes dominant at high energies. By fitting this AMS-02 we can calculate expected concomitant rise boron-to-carbon ratio, as well antiprotons. If...
Abstract In the standard picture of Galactic cosmic rays, a diffuse flux high-energy gamma rays and neutrinos is produced from inelastic collisions cosmic-ray nuclei with interstellar gas. The neutrino guaranteed signal for observatories such as IceCube but has not been found yet. Experimental searches this constitute an important test rays. Both observation nonobservation would allow implications physics acceleration transport. We present CRINGE , new model neutrinos, fitted to recent data...
The excess in the positron fraction measured by PAMELA has been interpreted as due to annihilation or decay of dark matter Galaxy. More prosaically it ascribed direct production positrons nearby pulsars pion during diffusive shock acceleration hadronic cosmic rays sources. We point out that measurements secondary ray nuclei can discriminate between these possibilities. New data on titanium-to-iron ratio support source model above and enable a prediction for boron-to-carbon at energies 100 GeV.
Gamma-ray data from Fermi-LAT reveal a bi-lobular structure extending up to 50 degrees above and below the galactic centre, which presumably originated in some form of energy release there less than few million years ago. It has been argued that gamma-rays arise hadronic interactions high cosmic rays are advected out by strong wind, or inverse-Compton scattering relativistic electrons accelerated at plasma shocks present bubbles. We explore alternative possibility undergoing stochastic...
Improved limits as well tentative claims for dark matter annihilation into γ-ray lines have been presented recently. We study the direct detection cross section induced from two photons in a model-independent fashion, assuming no additional couplings between and nuclei. find striking non-standard recoil spectrum due to different destructively interfering contributions nucleus scattering section. While case of s-wave current sensitivity experiments is insufficient compete with indirect...
We investigate possible imprints of galactic foreground structures such as the "radio loops" in derived maps cosmic microwave background. Surprisingly, there is evidence for these not only at radio frequencies through their synchrotron radiation, but also where emission by dust dominates. This suggests mechanism magnetic dipole radiation from grains enriched metallic iron or ferrimagnetic molecules. new we have identified present high latitudes, and potentially dominates over expected B-mode...
In the standard diffusive picture for transport of cosmic rays (CRs), a gradient in CR density induces typically small, dipolar anisotropy their arrival directions. This is being widely advertised as tool finding nearby sources. However, predicted dipole amplitude at TeV and PeV energies exceeds measured one by almost 2 orders magnitude. Here, we critically examine validity this prediction, which based on averaging over an ensemble turbulent magnetic fields. We focus (1) deviations...
A critical review of the standard paradigm for origin Galactic cosmic rays (CRs) is presented. Recent measurements local and far-away CRs reveal unexpected behaviors, which challenge commonly accepted scenario. These recent findings are discussed, together with long-standing open issues. Despite progress made thanks to ever-improving observational techniques theoretical investigations, at present our understanding behavior remains incomplete. We believe it still unclear whether a...
Measurements of the cosmic ray antiproton spectrum can be used to search for contributions from annihilating dark matter and constrain annihilation cross section. Depending on assumptions made regarding propagation in Galaxy, such constraints quite stringent. We revisit this topic, utilizing a set models fit boron, carbon, oxygen beryllium data. derive upper limits section find that when parameters are treated as nuisance (as we argue is appropriate), resulting significantly less stringent...
Modelling of cosmic ray transport and interpretation data ultimately rely on a solid understanding the interactions charged particles with turbulent magnetic fields. The paradigm over last 50 years has been so-called quasi-linear theory, despite some well-known issues. In absence widely accepted extension wave-particle must also be studied in numerical simulations where equations motion are directly solved realisation field. applications such test particle rays manifold: testing theories,...
Data from the Voyager probes have provided us with first measurement of cosmic ray intensities at MeV energies, an energy range that had previously not been explored. Simple extrapolations models fit data GeV e.g., AMS-02, however, fail to reproduce in predicted are too high. Oftentimes, this discrepancy is addressed by adding a break source spectrum or diffusion coefficient ad hoc fashion, convincing physical explanation yet be provided. Here, we argue discrete nature sources, which usually...
This paper demonstrates that a stochastic, rather than uniform, injection rate of MeV cosmic rays from supernovae can successfully model the observed ionization distribution for Galactic molecular clouds.
The arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It has been argued that this small-scale structure can naturally arise from ray scattering in local turbulent magnetic fields distort a global dipole anisotropy set by diffusion. We study effect terms the power spectrum and strength is related to properties relative provide formalism for how these spectra be inferred simulations motivate simple analytic extension ensemble-averaged diffusion...
The standard cosmological model predicts the existence of a Cosmic Neutrino Background, which has not yet been observed directly. Some experiments aiming at its detection are currently under development, despite tiny kinetic energy relic neutrinos, makes this task incredibly challenging. Since massive neutrinos attracted by gravitational potential our Galaxy, they can cluster locally. Neutrinos should be more abundant Earth position than an average point in Universe. This fact may enhance...
The spectrum of cosmic-ray electrons depends sensitively on the history and spatial distribution nearby sources. Given our limited observational handle sources, any model remains necessarily probabilistic. Previously, predictions were performed in a Monte Carlo fashion, summing contributions from individual, simulated sources to generate samples statistical ensemble possible electron spectra. Such simulations need be re-run if transport parameters (e.g. diffusion coefficient, maximum energy)...
Abstract Supernova remnants (SNRs) have long been suspected to be the primary sources of Galactic cosmic rays. Over past decades, great strides made in modeling particle acceleration, magnetic field amplification, and escape from SNRs. Yet while many SNRs observed nonthermal emission radio, X-rays, gamma rays, there is no evidence for any individual object contributing locally flux. Here, we propose a particular spectral signature that due energy-dependent For young nearby sources, predict...
We present a new model of the diffuse Galactic synchrotron radiation, concentrating on its angular anisotropies. While previous studies have focussed either variation emissivity large (kpc) scales, or fluctuations due to MHD turbulence in interstellar medium, we unify these approaches match power spectrum. note that usual cascade calculation ignores spatial correlations at injection scale compression medium by old supernova remnants -- 'radio loops', only four which are visible eye radio...
Until fairly recently, it was widely accepted that local cosmic-ray spectra were largely featureless power laws, containing limited information about their acceleration and transport. This viewpoint is currently being revised in light of evidence for a variety spectral breaks the fluxes nuclei. Here, we focus on electrons positrons which at highest energies must be origin due to strong radiative losses. We consider pure diffusion model Galactic transport determine its free parameters by...
Despite significant efforts over the past decade, origin of cosmic ray positron excess has still not been unambiguously established. A popular class candidate sources are pulsars or pulsar wind nebulae but these cannot also account for observed hard spectrum antiprotons. We revisit alternative possibility that high-energy positrons secondaries created by spallation in supernova remnants during diffusive shock acceleration primary rays, which further accelerated same shocks. The resulting...
Context. The spatial distribution of the gaseous components Milky Way is great importance for a number different fields, example, Galactic structure, star formation, and cosmic rays. However, obtaining distance information to clouds in interstellar medium from Doppler-shifted line emission notoriously difficult given our vantage point Galaxy. It requires knowledge gas velocities generally suffers ambiguities. Aims. Previous works often assumed optically thin limit (no absorption), had fixed...