We summarise the results found following a study of the effects that Galactic magnetic fields can have on the propagation of cosmic rays from local extragalactic sources. This study focuses on the coherent structures in the Jansson-Farrar Galactic magnetic field model, namely the: disk field, a toroidal field, and an x-field components. The phenomena of Galactic magnetic field shadowing, source deflection, and Galactic magnetic field tunnel vision are all noted. Attention throughout this study is placed on particles with rigidity around $10^{18.5}$ EV, believed to dominate the cosmic ray spectrum above the ankle. The Galactic magnetic field component predominantly responsible for giving rise to each of these different effects was determined.
Earliest AUGER UHECR anisotropy correlated with AGN within a GZK Universe almost fade away. Recent UHECR mass compositions did show a negligible nucleon composition and an UHECR nuclei (light or heavy) signature. The absence of UHECR events toward the Virgo cluster, an unique spread clustering of events around Cen-A, our nearest AGN, suggested a He-like nuclei as the main extragalactic UHECR component from Cen A, coexisting with Auger and HIRES composition. Because the light nuclei fragility such He UHECR cannot arrive from Virgo. Multiplet at twenty EeV along Cen A recently discovered by Auge…
UHECR (Ultra High Cosmic Rays) made by He-like lightest nuclei might solve the AUGER extragalactic clustering along Cen A: He UHECR cannot arrive from Virgo because the light nuclei fragility and opacity above few Mpc; UHECR signals are clustering along Cen-A spreading as observed by horizontal galactic arms magnetic fields, along random vertical angles [18]. Cen A events by He-like spread along a width angle as large as the observed clustered one. UHECR He, being fragile should partially fragment in secondaries at tens EeV multiplet (D,He3,p) almost as it occurs in the very recent UHECR multi…
A consequence of Liouville's theorem indicates that the recently observed large scale anisotropy in the arrival direction of Ultra-High-Energy Cosmic Rays (UHECRs) cannot be produced by the Galactic magnetic field, thus this anisotropy already needs to be present outside our Galaxy. But in this case, the observed energy spectrum and composition of UHECRs differs from the one outside of the Milky Way, due to the suppression or the amplification of the UHECR flux from certain directions by the Galactic magnetic field. In this work, we investigate this effect for the case of a dipole and a quadru…
We consider the synchrotron emission from electrons out in the Galactic halo bubble region where the Fermi bubble structures reside. Utilising a simple analytical expression for the non-thermal electron distribution and a toy magnetic field model, we simulate polarised synchrotron emission maps at a frequency of 30~GHz. Comparing these maps with observational data, we obtain constraints on the parameters of our toy Galactic halo bubble magnetic field model. Utilising this parameter value range for the toy magnetic field model, we determine the corresponding range of arrival directions and supp…
We review the experimental evidences about flux and mass composition of ultra high energy cosmic rays in connection with theoretical scenarios concerning astrophysical sources. In this context, we also address the discussion about the expected transition between cosmic rays produced inside the Galaxy and those coming from the intergalactic space.
The propagation trajectories of ultra-high-energy cosmic rays (UHECRs) are inevitably affected by Galactic magnetic field (GMF). Because of the inevitability, the importance of the studies of the propagation in GMF have increased to interpret the results of recent UHECR experiments. This article reviews the effects of GMF to the propagation and arrival directions of UHECRs and introduces recent studies to constrain UHECR sources.
We predict the arrival direction distribution of cosmic rays including their deflection in the Galactic magnetic field, for several combinations of source and composition hypotheses: the sources are hard X-ray AGNs or uniformly sample the matter distribution of galaxies, and the composition at the source is pure proton or is the Galactic cosmic ray composition measured by CREAM. We use the regular component of the Jansson-Farrar 2012 model for the GMF and allow for rigidities as low as 2 EeV. We report the correlations of published UHECRs, rescaling event energies so as to reconcile the spectr…
We update the constraints on the location of the nearest UHECR source. By analyzing recent data from the Pierre Auger Observatory using state-of-the-art CR propagation models, we reaffirm the need of local sources with a distance less than 25-100 Mpc, depending on mass composition. A new fast semi-analytical method for the propagation of UHECR in environments with turbulent magnetic fields is developed. The onset of an enhancement and a low-energy magnetic horizon of cosmic rays from sources located within a particular distance range is demonstrated. We investigate the distance to the nearest …
We study the possibility that the $γ$-ray loud active galactic nuclei (AGN) are the sources of ultra-high energy cosmic rays (UHECR), through the correlation analysis of their locations and the arrival directions of UHECR. We use the $γ$-ray loud AGN with $d\le 100 {\rm Mpc}$ from the second Fermi Large Area Telescope AGN catalog and the UHECR data with $E\ge 55 {\rm EeV}$ observed by Pierre Auger Observatory. The distribution of arrival directions expected from the $γ$-ray loud AGN is compared with that of the observed UHECR using the correlational angular distance distribution and the Kolmog…
We study possible correlations between ultrahigh energy cosmic rays (UHECRs), observed by Auger, AGASA and Yakutsk, and nearby active galactic nuclei (AGNs) and $Fermi$ sources. We consider the deflection effects by a Galactic magnetic field (GMF) model constrained by the most updated measurements. We found that the average deflection angles of UHECRs by the Galactic magnetic fields are less than $4^\circ$. A correlation between the Auger cosmic-ray events and nearby AGNs with a significance level of $\sim 4σ$ was found for the Auger UHECR data sets with or without deflection correction. No co…
A good model of the Galactic magnetic field is crucial for estimating the Galactic contribution in dark matter and CMB-cosmology studies, determining the sources of UHECRs, and also modeling the transport of Galactic CRs since the halo field provides an important escape route for by diffusion along its field lines. We briefly review the observational foundations of the Jansson-Farrar 2012 model for the large scale structure of the GMF, underscoring the robust evidence for a N-to-S directed, spiraling halo field. New results on the lensing effect of the GMF on UHECRs are presented, displaying m…
We discuss a representative selection of particle acceleration mechanisms believed to be operating in Active Galactic Nuclei. Starting from direct electrostatic field acceleration in the vicinity of the black hole up to Fermi-type particle acceleration in the jet and beyond, possible efficiency constraints on the energization of ultra-high energy cosmic rays (UHECR) are evaluated. When paradigmatically applied to Cen A, the following results are obtained: (i) Proton acceleration to energies of $E_c = 5\times 10^{19}$ eV and beyond remains challenging and most likely requires the operation of a…
We evaluate the validity of leading models of the Galactic magnetic field for predicting UHECR deflections from Cen A. The Jansson-Farrar 2012 GMF model (JF12), which includes striated and random components as well as an out-of-plane contribution to the regular field not considered in other models, gives by far the best fit globally to all-sky data including the WMAP7 22 GHz synchrotron emission maps for Q, U, and I and ~40,000$ extragalactic Rotation Measures (RMs). Here we test the models specifically in the Cen A region, using 160 well-measured RMs and the Polarized Intensity from WMAP, nea…
We report results of the first comprehensive, high resolution study of the deflections of UHECRs using a realistic model of the Galactic magnetic field and extending to sufficiently low rigidities, R = E/Z = 10^18 V, to describe Fe in the UHE energy range or the mixed composition reported by the Pierre Auger Collaboration at the energy of the observed dipole anisotropy. We use the Jansson-Farrar (JF12) model, which has both large scale coherent and a structured random components, and determine deflections for fifteen rigidities from 10^18.0 to 10^20.0 V, for L_coh = 30 pc and 100 pc. We check …
The origin and composition of Ultra-High Energy Cosmic Ray Events (UHECRs) are under debate. Here we improve constraints on the source population(s) and compositions of UHECRs by accounting for UHECR deflections within existing Galactic magnetic field models (GMFs). We used Monte Carlo simulations for UHECRs detected by the Pierre Auger Observatory and AGASA in order to determine their outside-the-Galaxy arrival directions, and compared these with Galactic and extragalactic sources. The simulations, which used UHECR compositions from protons to Iron and seven models of the ordered GMF, include…
We investigate the production of ultra-high-energy cosmic ray (UHECR) in relativistic jets from low-luminosity active galactic nuclei (LLAGN). We start by proposing a model for the UHECR contribution from the black holes (BHs) in LLAGN, which present a jet power $P_{\mathrm{j}} \leqslant 10^{46}$ erg s$^{-1}$. This is in contrast to the opinion that only high-luminosity AGN can accelerate particles to energies $ \geqslant 50$ EeV. We rewrite the equations which describe the synchrotron self-absorbed emission of a non-thermal particle distribution to obtain the observed radio flux density from …
Ultra-high energy cosmic rays (UHECRs) may be produced in active galactic nuclei (AGN) or gamma-ray burst (GRB) jets. I argue that magnetic reconnection in jets can accelerate UHECRs rather independently of physical processes in the magnetic dissipation region. First order Fermi acceleration can efficiently take place in the region where the unreconnected (upstream) magnetized fluid converges into the reconnection layer. I find that protons can reach energies up to E~10^{20} eV in GRB and powerful AGN jets while iron nuclei can reach similar energies in AGN jets of more moderate luminosity.
We propose a new method for the estimation of ultra-high energy cosmic ray (UHECR) mass composition from a distribution of their arrival directions. The method employs a test statistic (TS) based on a characteristic deflection of UHECR events with respect to the distribution of luminous matter in the local Universe. Making realistic simulations of the mock UHECR sets, we show that this TS is robust to the presence of galactic and non-extreme extra-galactic magnetic fields and sensitive to the mass composition of events in a set. This allows one to constrain the UHECR mass composition by compar…
Ultra High Cosmic Rays (UHECR) should be tracing their sources, making a new astronomy. Their events counting are finally growing, by Auger experiment, into cosmic sky. Their map should follow the mass distribution in a narrow cosmic volume (the GZK cut off region, correlated with Super Galactic Plane (SPG) or Local Group) if they were protons, as most expected. Recently the last 69 UHECR did not longer follow the SGP map, opening the way to very different correlations, and extreme bending connection; we reconfirm here our Lightest Nuclei interpretation, while showing here the last event over …
Active galactic nuclei (AGN) are considered as one of the most appropriate sources of cosmic rays with energy exceeding $\sim 10^{18}$ eV. Virgo A (M87 or NGC 4486) is the second closest to the Milky Way active galaxy. According to existing estimations it can be a prominent source of ultra high energy cosmic rays (UHECR). However not many events have been registered in the sky region near Virgo A, possibly due to magnetic field influence. In the present work we check UHECR events from the recent sets of data (AUGER, Telescope Array etc.) for possibility of their origination in this AGN. We car…
Active Galactic Nuclei (AGNs) and their relativistic jets belong to the most promising class of ultra-high-energy cosmic ray (UHECR) accelerators. This compact review summarises basic experimental findings by recent instruments, and discusses possible interpretations and astrophysical constraints on source energetics. Particular attention is given to potential sites and mechanisms of UHECR acceleration in AGNs, including gap-type particle acceleration close to the black hole, as well as first-order Fermi acceleration at trans-relativistic shocks and stochastic shear particle acceleration in la…
We develop the statistical methods for comparing two sets of arrival directions of cosmic rays in which the two-dimensional distribution of arrival directions is reduced to the one-dimensional distributions so that the standard one-dimensional Kolmogorov-Smirnov test can be applied. Then we apply them to the analysis of correlation between the ultra-high energy cosmic rays (UHECR) with energies above $5.7\times10^{19}$ eV, observed by Pierre Auger Observatory (PAO) and Akeno Giant Air Shower Array (AGASA), and the active galactic nuclei (AGN) within the distance 100 Mpc. For statistical test, …
We update the previous analysis of correlation between ultra-high energy cosmic rays (UHECR) and active galactic nuclei (AGN), using 69 UHECR events with energy $E\ge55\,{\rm EeV}$ released in 2010 by Pierre Auger observatory and 862 AGN within the distance $d\le100\,{\rm Mpc}$ listed in the 13th edition of Véron-Cetty and Véron AGN catalog. To make the test hypothesis definite, we use the simple AGN source model in which UHECR are originated both from AGN, with the fraction $f_A$, and from the isotropic background. We treat all AGN as equal sources of UHECR, and introduce the smearing angle $…
Ultra High Energy Cosmic Rays, UHECR, maybe protons, as most still believe and claim, or nuclei; in particular lightest nuclei as we advocated recently. The first (Auger Collaboration) nucleon proposal (2007)[2] foresaw to trace clearly the UHECR GZK Universe reaching far (up to 100 Mpc) Super-Galactic-Plane, with little angular dispersion. On the contrary Lightest Nuclei model (2008)[3], inspired by observed composition and by nearest CenA clustering (almost a quarter of the AUGER events) explains a modest and narrow (few Mpc) Universe view, as well as the puzzling Virgo absence: lightest nuc…
It is suggested that essentially all of the UHECRs we detect, including those at the highest energy, originate in our Galaxy. It is shown that even if the density of sources decreases with Galactic radius, then the anisotropy and composition can be understood. Inward anisotropy, as recently reported by the Auger collaboration can be understood as drift along the current sheet of UHECRs originating outside the solar circle, as predicted in Kumar and Eichler (2014), while those originating within the solar circle exit the Galaxy at high latitudes.
We have built regions in a Sky map where it should be expected the arrival of 120 EeV ultrahigh energy cosmic rays (UHECR) directionally correlated with the latest astrophysical neutrino tracks observed at IceCube, which are taken as point sources. In order to calculate these arrival directions we have considered contributions to the cosmic rays deflections originated by the galactic and the extragalactic magnetic field, and a UHECR composition compatible with the current expectations. We have used the Jansson-Farrar JF12 model for the Galactic magnetic field and an extragalactic magnetic fiel…
Auger data show evidence for a correlation between ultrahigh-energy cosmic rays (UHECRs) and nearby starburst galaxies. This intriguing correlation is consistent with data collected by the Telescope Array, which have revealed a much more pronounced directional ``hot spot'' in arrival directions not far from the starburst galaxy M82. In this work, we assume starbursts are sources of UHECRs and investigate the prospects to use the observed distribution of UHECR arrival directions to constrain Galactic magnetic field models. We show that if the Telescope Array hot spot indeed originates from M82,…
Ultra High Cosmic Rays) made by He-like lightest nuclei might solve the AUGER extragalactic clustering along Cen A. Moreover He like UHECR nuclei cannot arrive from Virgo because the light nuclei fragility and opacity above a few Mpc, explaining the Virgo UHECR absence. UHECR signals are spreading along Cen-A as observed because horizontal galactic arms magnetic fields, bending them on vertical angles. Cen A events by He-like nuclei are deflected as much as the observed clustered ones; proton will be more collimated while heavy (iron) nuclei are too much dispersed. Such a light nuclei UHECR co…
The rise of nucleon UHECR above GZK astronomy made by protons is puzzled by three main mysteries: an unexpected nearby Virgo UHECR suppression, a rich crowded clustering frozen vertically (north-south) along Cen A, a composition suggesting nuclei and not nucleons. The UHECR map, initially consistent with GZK volumes, to day seem to be not much correlated with expected Super Galactic Plane. Moreover slant depth data of UHECR from AUGER airshower shape do not favor the proton but points to a nuclei, while HIRES, on the contrary favors mostly nucleons. We tried to solve the contradictions assumin…
We use the Jansson-Farrar JF12 magnetic field configuration in the context of point source searches by correlating the Telescope Array ultra-high energy cosmic ray data and the IceCube-40 neutrino candidates. As expected, we have found no correlations, thus, we devote this paper to the study of the effect of different magnetic field hypotheses on the minimum neutrino source flux strength required for a $5σ$ discovery and the derived $90\%$ CL upper limits. In this study we present a comparison between the JF12 field, that includes a combination of regular and random field components, and the s…
Recent results from Pierre Auger Observatory, showing energy dependent chemical composition of ultrahigh-energy cosmic rays (UHECRs) with a growing fraction of heavy elements at high energies, suggest a possible non-negligible contribution of the Galactic sources. We show that, in the case of UHECRs produced by gamma-ray bursts (GRBs) or rare types of supernova explosions that took place in Milky Way in the past, the change in UHECR composition can result from the difference in diffusion times for different species. The anisotropy in the direction of the Galactic Center is expected to be a few…
Anisotropy in the arrival direction distribution of ultrahigh-energy cosmic rays (UHECRs) produced by powerful sources is numerically evaluated. We show that, taking account of the Galactic magnetic field, nondetection of significant anisotropy at $\approx 10^{19}$ eV at present and in future experiments imposes general upper limits on UHECR proton luminosity of steady sources as a function of source redshifts. The upper limits constrain the existence of typical steady sources in the local universe and limit the local density of $10^{19}$ eV UHECR sources to be $\gtrsim 10^{-3}$ Mpc$^{-3},$ as…
Modern observatories of ultra-high energy cosmic rays (UHECR) have collected over 10^4 events with energies above 10 EeV, whose arrival directions appear to be nearly isotropically distributed. On the other hand, the distribution of matter in the nearby Universe -- and, therefore, presumably also that of UHECR sources -- is not homogeneous. This is expected to leave an imprint on the angular distribution of UHECR arrival directions, though deflections by cosmic magnetic fields can confound the picture. In this work, we investigate quantitatively this apparent inconsistency. To this end we stud…
Four UHECRs in the combined HiRes and AGASA datasets are backtracked in the Galactic magnetic field. They point to a common source which is localized to within 1 degree, if they are protons as is shown to be the most probable charge assignment. A Swift-BAT hard X-ray AGN in the galaxy CGCG 291-028 is the only notable source candidate within the source locus and within the GZK distance horizon. The spectrum of the four events is consistent with production in a transient event such as a stellar tidal disruption flare. Under the assumption the UHECRs were produced in CGCG 291-028, the total energ…
Pierre Auger observatory reported the distribution of arrival directions of the highest energy cosmic rays. These events were collected in 10 years of operations with declinations between -90$^\circ$ and +45$^\circ$. The IceCube neutrino telescope reported the detection of 82 extraterrestrial neutrinos in the High-Energy Starting Events catalog. The highest-energy neutrino event (IC35) reported in this catalog had an energy of 2004$^{+236}_{-262}$ TeV and its reconstruction was centered at RA=$208.4^\circ$ and DEC=$-55.8^\circ$ (J2000). Being Centaurus A the nearest radio-loud active Galactic …
We present a bottom-up calculation of the flux of ultra-high energy cosmic rays (UHECRs) and high-energy neutrinos produced by powerful jets of active galactic nuclei (AGNs). By propagating test particles in 3D relativistic magnetohydrodynamic jet simulations, including a Monte Carlo treatment of sub-grid pitch-angle scattering and attenuation losses due to realistic photon fields, we study the spectrum and composition of the accelerated UHECRs and estimate the amount of neutrinos produced in such sources. We find that UHECRs may not be significantly affected by photodisintegration in AGN jets…
We investigated the possibility of acceleration of ultra-high-energy cosmic rays (UHECRs) in nearby active galactic nuclei (AGNs) using archival multi-wavelength observational data, and then we constrained their physical conditions, i.e., the luminosity of the synchrotron radiation and the size of the acceleration site. First, we investigated the spatial correlation between the arrival directions of UHECRs and the positions of nearby AGNs in the Fermi third gamma-ray source catalog. We selected 27 AGNs as candidates of accelerators of UHECRs. Then, we evaluated the physical conditions in the a…
Motivated by the ~7 % dipole anisotropy in the distribution of ultra-high energy cosmic-rays (UHECRs) above 8 EeV, we explore the anisotropy induced by the large scale structure, using constrained simulations of the local Universe and taking into account the effect of magnetic fields. The value of the intergalactic magnetic field (IGMF) is critical as it determines the UHECR cosmic horizon. We calculate the UHECR sky maps for different values of the IGMF variance and show the effect of the UHECR horizon on the observed anisotropy. The footprint of the local ($\lesssim350$ Mpc) Universe on the …
We have used recently published data from the Pierre Auger Observatory and the Telescope Array Project to conclude some inferences concerning the origin and composition of ultra high-energy cosmic rays (UHECR). We advocate for model the UHECR flux as a combination of the Galactic and Extragalactic components exchanging the dominant role at the famous feature of the energy spectrum called 'the ankle'. We put a special emphasis on the individual experiment energy resolution and possible biases it introduces. We have eventually combined the data from both big experiments to the one 'world average…
With the publicly available astrophysical simulation framework for propagating extraterrestrial UHE particles, CRPropa 3, it is now possible to study realistic UHECR source scenarios including deflections in Galactic and extragalactic magnetic fields in an efficient way. Here we discuss three recent studies that have already been done in that direction. The first one investigates what can be expected in the case of maximum allowed intergalactic magnetic fields. Here is shown that, even if voids contain strong magnetic fields, deflections of protons with energies $\gtrsim 60 \; \text{EeV}$ from…
The origin and composition of ultra-high energy cosmic rays (UHECRs) remain a mystery. The common lore is that UHECRs are deflected from their primary directions by the Galactic and extragalactic magnetic fields. Here we describe an extragalactic contribution to the deflection of UHECRs that does not depend on the strength and orientation of the initial seed field. Using the IllustrisTNG simulations, we show that outflow-driven magnetic bubbles created by feedback processes during galaxy formation deflect approximately half of all $10^{20}$ eV protons by $1^{\circ}$ or more, and up to $20$-$30…
We analyze the correlation of the positions of gamma-ray sources in the Fermi Large Area Telescope First Source Catalog (1FGL) and the First LAT Active Galactic Nuclei (AGN) Catalog (1LAC) with the arrival directions of ultra-high-energy cosmic rays (UHECRs) observed with the Pierre Auger Observatory, in order to investigate the origin of UHECRs. We find that Galactic sources and blazars identified in the 1FGL are not significantly correlated with UHECRs, while the 1LAC sources display a mild correlation (2.6 sigma level) on a ~2.4 degree angular scale. When selecting only the 1LAC AGNs closer…
Recent evidence from the Pierre Auger Observatory suggests a transition, at 5 EeV-10EeV in the composition of Ultra High Energy Cosmic Rays (UHECRs), from protons to heavier nuclei such as iron. I consider here the implications of the heavier composition on the sources of UHECRs. The smaller magnetic rigidity implies that nuclei UHECRs are: (i) More easily accelerated (ii) Local, as they can diffuse only a few Mpc from their sources before disintegrating (iii) Isotropic, because large deflections in the extra galactic and the galactic magnetic fields erase the directional information. Uncertai…
