Anisotropies of ultra-high energy cosmic rays dominated by a single source in the presence of deflections

Dundovic, A.; Sigl, Günter

doi:10.1088/1475-7516/2019/01/018

Cited by 13 publications

(12 citation statements)

References 62 publications

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“…This was previously studied in Refs. [15][16][17][18]. We consider a discrete distribution of sources described by the distance to the nearest source, D min , in such a way that the number of sources in a shell with distance iD min is i 2 .…”

Section: Dipole Of An Ensemble Of Sourcesmentioning

confidence: 99%

Ultrahigh-energy cosmic rays dipole and beyond

Lang

Taylor²,

Souza

2021

Phys. Rev. D

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Recent data from the Pierre Auger Observatory has revealed the presence of a large-scale dipole in the arrival direction distribution of ultrahigh-energy cosmic rays (UHECR). In this work, we build up an understanding of the diffusive origin of such a dipolar behavior as well as its dependency on energy and astrophysical source assumptions such as extra-Galactic magnetic field strength and cosmic ray composition. We present a novel analytical approach for calculating the angular distribution of CR coming from a single source and discuss the regimes in which the steady-state dipole result is expected. We also present a semianalytical method for calculating the evolution with energy of the resultant dipole for an ensemble of sources. We show that a local source allows for a strong growth of the dipole with energy over a large energy range. The possibility of a transition from a dipolar to nondipolar regime at the highest energies and its implications for the source density, magnetic field intensity, and cosmic ray composition are discussed.

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Section: Dipole Of An Ensemble Of Sourcesmentioning

confidence: 99%

Ultrahigh-energy cosmic rays dipole and beyond

Lang

Taylor²,

Souza

2021

Phys. Rev. D

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“…In order to obtain suitable statistics, an observer sphere with a radius of r obs = 100 kpc is chosen. This size also ensures, that no significant deformation of the higher multipole moments of the arrival directions occurs, as recently shown by Dundović and Sigl [100]. Thus, UHECR candidates are only propagated on extragalactic scales at first.…”

Section: Simulation Setupmentioning

confidence: 61%

Ultra-high-energy cosmic rays from radio galaxies

Eichmann

Rachen

Merten

et al. 2018

J. Cosmol. Astropart. Phys.

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Radio galaxies are intensively discussed as the sources of cosmic rays observed above about 3 × 10 18 eV, called ultra-high energy cosmic rays (UHECRs). We present a first, systematic approach that takes the individual characteristics of these sources into account, as well as the impact of the extragalactic magnetic-field structures up to a distance of 120 Mpc. We use a mixed simulation setup, based on 3D simulations of UHECRs ejected by observed, individual radio galaxies taken out to a distance of 120 Mpc, and on 1D simulations over a continuous source distribution contributing from beyond 120 Mpc. Additionally, we include the ultra-luminous radio galaxy Cygnus A at a distance of about 250 Mpc, as its contribution is so strong that it must be considered as an individual point source. The implementation of the UHECR ejection in our simulation setup, both that of individual radio galaxies and the continuous source function, is based on a detailed consideration of the physics of radio jets and standard first-order Fermi acceleration. This allows to derive the spectrum of ejected UHECR as a function of radio luminosity, and at the same time provides an absolute normalization of the problem involving only a small set of parameters adjustable within narrow constraints.We show that the average contribution of radio galaxies taken over a very large volume cannot explain the observed features of UHECRs measured at Earth. However, we obtain excellent agreement with the spectrum, composition, and arrival-direction distribution of UHECRs measured by the Pierre Auger Observatory, if we assume that most UHECRs observed arise from only two sources: The ultra-luminous radio galaxy Cygnus A, providing a mostly light composition of nuclear species dominating up to about 6 × 10 19 eV, and the nearest radio galaxy Centaurus A, providing a heavy composition dominating above 6 × 10 19 eV.Here we have to assume that extragalactic magnetic fields out to 250 Mpc, which we did not include in the simulation, are able to isotropize the UHECR events at about 8 EeV arriving from Cygnus A. Even in this case, significant anisotropy correlated with Cygnus A and Centaurus A could be present at higher energies, and thus allow for differences in UHECR spectrum and composition between the northern and southern hemispheres. If this scenario can be confirmed, it would also imply that the UHECR flux in our local cosmic environment is significantly above the average throughout the universe.

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“…Several works have tried to model the arising of the dipole and its evolution with energy [6][7][8][9][10]. These models usually rely on Monte Carlo simulations for the propagation of UHECR.…”

Section: Introductionmentioning

confidence: 99%

The origin of UHECR: the distance to the nearest source and the dipole

Lang¹,

Taylor²,

Souza³

2021

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)

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A semi-analytical, fast and robust method for the propagation of ultra-high-energy cosmic rays (UHECR) under extra-galactic turbulent magnetic fields presented by the authors in previous works is described in detail. Under the assumption of dominant turbulent fields, it is possible to obtain the energy spectrum, as well as the relative contribution from each source, and the angular distribution of arrival directions without the need for 4-D simulations. This method provides an important tool in the quest for the origin of UHECR. A brief overview of the results already obtained with it is presented. The relative contribution to the energy spectrum from sources in different distance shells is elucidated and constraints of a few tens of Mpc, depending on composition, are imposed to the distance to the nearest source. A solid understanding of the arising of the dipole as well as its evolution with energy is built. The importance of a power spectrum analysis in energies detected by experiments is discussed.

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Anisotropies of ultra-high energy cosmic rays dominated by a single source in the presence of deflections

Cited by 13 publications

References 62 publications

Ultrahigh-energy cosmic rays dipole and beyond

Ultrahigh-energy cosmic rays dipole and beyond

Ultra-high-energy cosmic rays from radio galaxies

The origin of UHECR: the distance to the nearest source and the dipole

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