What can be learnt from UHECR anisotropies observations? Paper I : large-scale anisotropies and composition features

Abstract

We investigate the implications of the current data regarding large scale anisotropies, and examine to what extent they can be used to constrain the origin of UHECRs and the astrophysical parameters of the source scenarios. We discuss the possibility of observing an associated anisotropy of the composition, the potential benefit of the separation of the different nuclear components and the interest of observing the UHECR sky with larger exposure future observatories. We simulate UHECR sky maps for various astrophysical scenarios satisfying the current observational constraints, taking into account the energy losses of the UHE protons and nuclei and their deflections by intervening magnetic fields. We investigate scenarios in which the UHECR source distribution follows that of the galaxies, varying the source composition and spectrum, the source density and the magnetic field models. We apply similar analyses as those used by the Auger collaboration. We find that: i) reproducing the observed dipole anisotropy and its energy evolution is relatively easy within our assumptions; ii) this agreement can be obtained with different sets of assumptions on the astrophysical parameters, and is thus not, at this stage, very constraining for UHECR source scenarios; iii) the actual reconstructed direction of the dipole appears non natural in essentially all scenarios investigated, and challenges their main assumptions on the source distribution or the assumed magnetic field configuration, especially in the Galaxy; iv) except for protons, the energy range in which the GZK horizon strongly reduces is a key target for anisotropy searches for each given nuclear species; v) The composition anisotropy naturally expected in our models is unlikely to account for that recently reported by Auger unless the observed amplitude is a strong positive statistical fluctuation of an intrinsically weaker signal.

arXiv comment39 pages, 32 figures

References in corpus (79)

• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• EPOS LHC : test of collective hadronization with LHC data
• Correlation of the highest energy cosmic rays with nearby extragalactic objects
• The 2MASS Redshift Survey - Description and Data Release
• A New Model of the Galactic Magnetic Field
• Updated Nearby Galaxy Catalog
• Cosmicflows-3
• Parton Ladder Splitting and the Rapidity Dependence of Transverse Momentum Spectra in Deuteron-Gold Collisions at RHIC
• Observation of a Large-scale Anisotropy in the Arrival Directions of Cosmic Rays above $8\times 10^{18}$ eV
• The surface detector array of the Telescope Array experiment
• Depth of Maximum of Air-Shower Profiles at the Pierre Auger Observatory: Measurements at Energies above 10^17.8 eV
• Radio observational constraints on Galactic 3D-emission models
• Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment
• Combined fit of spectrum and composition data as measured by the Pierre Auger Observatory
• Implications of Cosmological Gamma-Ray Absorption II. Modification of gamma-ray spectra
• Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
• The Galactic Magnetic Field
• The Laniakea supercluster of galaxies
• Depth of Maximum of Air-Shower Profiles at the Pierre Auger Observatory: Composition Implications
• The Giant Radio Array for Neutrino Detection (GRAND): Science and Design
• Deriving global structure of the Galactic Magnetic Field from Faraday Rotation Measures of extragalactic sources
• Cosmological Magnetic Fields Limits in an Inhomogeneous Universe
• Indication of anisotropy in arrival directions of ultra-high-energy cosmic rays through comparison to the flux pattern of extragalactic gamma-ray sources
• Groups of Galaxies in the Two Micron All-Sky Redshift Survey
• Improved predictions of nuclear reaction rates with the TALYS reaction code for astrophysical applications
• Galaxy Groups within 3500 km s${}^{-1}$
• Measurement of the cosmic-ray energy spectrum above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory
• Ultra high energy cosmic rays and the large scale structure of the galactic magnetic field
• Ultra-High Energy Cosmic Ray Probes of Large Scale Structure and Magnetic Fields
• Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition
• Cluster Analysis of Extremely High Energy Cosmic Rays in the Northern Sky
• An evaluation of the exposure in nadir observation of the JEM-EUSO mission
• UHE nuclei propagation and the interpretation of the ankle in the cosmic-ray spectrum
• Modelling the Galactic Magnetic Field on the Plane in 2D
• Extragalactic propagation of ultrahigh energy cosmic-rays
• Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum
• Extra-galactic magnetic fields and the second knee in the cosmic-ray spectrum
• Anisotropy vs chemical composition at ultra-high energies
• Diffusive propagation of UHECR and the propagation theorem
• UHECR acceleration at GRB internal shocks
• The Galactic halo magnetic field revisited
• Ultra-High Energy Cosmic Rays in a Structured and Magnetized Universe
• The toes of the ultra high energy cosmic ray spectrum
• A complete model of the CR spectrum and composition across the Galactic to Extragalactic transition
• On the Evidence for Clustering in the Arrival Directions of AGASA's Ultrahigh Energy Cosmic Rays
• Giant Dipole Resonance Parameters of Ground-State Photoabsorption: Experimental Values with Uncertainties
• Measurement of the fluctuations in the number of muons in extensive air showers with the Pierre Auger Observatory
• Propagation of high-energy cosmic rays in extragalactic turbulent magnetic fields: resulting energy spectrum and composition
• First Results of Fast One-dimensional Hybrid Simulation of EAS Using CONEX
• Simulations of ultra-high Energy Cosmic Rays in the local Universe and the origin of Cosmic Magnetic Fields
• The optical depth of the Universe to ultrahigh energy cosmic ray scattering in the magnetized large scale structure
• New constraints on modelling the random magnetic field of the MW
• The star formation history of galaxies: the role of galaxy mass, morphology and environment
• Role of Galactic sources and magnetic fields in forming the observed energy-dependent composition of ultrahigh-energy cosmic rays
• Inhomogeneous extragalactic magnetic fields and the second knee in the cosmic ray spectrum
• Connecting Synchrotron, Cosmic Rays, and Magnetic Fields in the Plane of the Galaxy
• The Imprint of Large Scale Structure on the Ultra-High-Energy Cosmic Ray Sky
• GZK horizon and magnetic fields
• Anisotropies of ultra-high energy cosmic ray nuclei diffusing from extragalactic sources
• Ultrahigh Energy Nuclei Propagation in a Structured, Magnetized Universe
• Ultrahigh energy cosmic rays from a nearby extragalactic source in the diffusive regime
• The Pierre Auger Observatory: Contributions to the 36th International Cosmic Ray Conference (ICRC 2019)
• Galactic Dynamos and Galactic Winds
• How do disks and planetary systems in high-mass open clusters differ from those around field stars?
• How isotropic can the UHECR flux be?
• The quasi-linear nearby Universe
• Anisotropy expectations for ultra-high-energy cosmic rays with future high statistics experiments
• Search for Large-scale Anisotropy on Arrival Directions of Ultra-high-energy Cosmic Rays Observed with the Telescope Array Experiment
• The GZK cutoff behind a Magnetized Universe
• GCOS -- The Global Cosmic Ray Observatory
• Cosmic-Ray Anisotropy from Large Scale Structure and the effect of magnetic horizons
• Generalised 3D-reconstruction method of a dipole anisotropy in cosmic-ray distributions
• Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory
• On the anisotropy in the arrival directions of ultra-high-energy cosmic rays
• The extragalactic ultra-high energy cosmic-ray dipole
• Covering the celestial sphere at ultra-high energies
• Progress in the Global Modeling of the Galactic Magnetic Field
• Can we reconcile the TA excess and hotspot with Auger observations?
• Anti-GZK effect in UHECR spectrum

Cited by in corpus (14)

• Constraining models for the origin of ultra-high-energy cosmic rays with a novel combined analysis of arrival directions, spectrum, and composition data measured at the Pierre Auger Observatory
• Active Galactic Nuclei as potential Sources of Ultra-High Energy Cosmic Rays
• Large-scale cosmic ray anisotropies with 19 years of data from the Pierre Auger Observatory
• Constraints on UHECR sources and extragalactic magnetic fields from directional anisotropies
• Ultra High Energy Cosmic Ray Source Models: Successes, Challenges and General Predictions
• What can be learnt from UHECR anisotropies observations Paper II: intermediate-scale anisotropies
• The large-scale anisotropy and flux (de-)magnification of ultra-high-energy cosmic rays in the Galactic magnetic field
• Case for Centaurus A as the main source of ultrahigh-energy cosmic rays
• Constraining ultra-high-energy cosmic ray composition through cross-correlations
• Update on the indication of a mass-dependent anisotropy above $10^{18.7}$eV in the hybrid data of the Pierre Auger Observatory
• Honing cross-correlation tools for inference on ultra-high-energy cosmic-ray composition
• Modeling Ultra-High-Energy Cosmic Rays propagation using the input from Configuration Interaction Shell Model
• Insights on the mass composition of ultrahigh-energy cosmic rays from small-scale anisotropy with large-scale structure simulations
• Neutrino anisotropy as a probe of extreme astrophysical accelerators