Large-scale Cosmic-Ray Anisotropies above 4 EeV Measured by the Pierre Auger Observatory

Aab, A.; Abreu, P.; Aglietta, M.; Albuquerque, I. F. M.; Albury, Justin M.; Allekotte, I.; Almela, A.; Castillo, J.; Álvarez-Muñiz, J.; Anastasi, Gioacchino Alex; Anchordoqui, Luis A.; Andrada, Belén; Andringa, S.; Aramo, C.; Asorey, H.; Assis, P.; Ávila, G.; Badescu, A. M.; Bălăceanu, Alexandru; Barbato, Felicia; Luz, Ricardo Jorge Barreira; Baur, S.; Becker, K. H.; Bellido, J. A.; Bérat, C.; Bertaina, M.; Bertou, X.; Biermann, P. L.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blažek, Jiří; Bleve, C.; Bohã̌cov́a, M.; Bonifazi, C.; Borodai, N.; Botti, Ana Martina; Brack, J.; Bretz, T.; Bridgeman, A.; Briechle, Florian Lukas; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, Mario; Caballero-Mora, K. S.; Caccianiga, Lorenzo; Calcagni, L.; Cancio, A.; Canfora, F.; Carceller, Juan Miguel; Caruso, R.; Castellina, A.; Catalani, Fernando; Cataldi, G.; Cazón, L.; Chinellato, J. A.; Chudoba, J.; Chytka, L.; Clay, R. W.; Cerutti, Agustín Cobos; Colalillo, R.; Coleman, Alan; Coluccia, M. R.; Conceição, R.; Consolati, G.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; Day, J. A.; Almeida, R. M. de; Jong, S. J. De; Mauro, G. De; Neto, J. R. T. de Mello; Mitri, I. De; Oliveira, Jaime de; Souza, Vítor de; Debatin, J.; Deligny, O.; Dhital, N.; Castro, M. L. Díaz; Diogo, F.; Dobrigkeit, C.; D’Olivo, J. C.; Dorosti, Q.; Anjos, Rita Cassia dos; Dova, M. T.; Dundovic, A.; Ebr, Jan; Engel, R.; Erdmann, M.; Escobar, C. O.; Etchegoyen, A.; Falcke, H.; Farmer, John; Farrar, Glennys R.; Fauth, A. C.; Fazzini, N.; Feldbusch, Fridtjof; Fenu, Francesco; Ferreyro, L.P.; Figueira, J. M.; Filipčić, A.; Freire, M. M.; Fujii, Toshihiro; Fuster, Alan; García, Beatriz; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glombitza, Jonas; Golup, G.; Berisso, M. Gómez; Vitale, Primo F. Gómez; González, Nicolás Martín; Goos, Isabel; Góra, Dariusz; Gorgi, A.; Gottowik, Marvin; Grubb, Trent D.; Guarino, F.; Guedes, G. P.; Guido, Eleonora; Halliday, R.; Hampel, Matías Rolf; Hansen, P.; Harari, D.; Harrison, T. A.; Harvey, Violet M.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horváth, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Johnsen, Jeffrey A.; Josebachuili, M.; Jurýšek, Jakub; Kääpä, Alex; Kampert, Karl-Heinz; Keilhauer, B.; Kemmerich, N.; Kemp, J.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Kuempel, D.; Mezek, G. Kukec; Awad, A. Kuotb; Lago, Bruno L.; LaHurd, D.; Lang, Rodrigo Guedes; Legumina, R.; Oliveira, M. A. Leigui de; Lenok, Vladimir; Letessier‐Selvon, A.; Lhenry-Yvon, I.; Presti, D. Lo; Lopes, L.; López, R.; Casado, A. López; Lorek, R.; Luce, Quentin; Lucero, A.; Malacari, M.; Mallamaci, M.; Mancarella, G.; Mandát, Dušan; Mantsch, P.; Mariazzi, A. G.; Maris, Ioana Codrina; Marsella, G.; Martello, D.; Martínez, H.; Bravo, O. Martínez; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthiae, G.; Mayotte, E.; Mazur, Péter; Medina‐Tanco, G.; Melo, D.; Menshikov, Alexander; Merenda, Kevin-Druis; Michal, Stanislav; Micheletti, M. I.; Middendorf, L.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, Silvia; Montanet, F.; Morello, C.; Morlino, G.; Mostafá, M.; Müller, Ana L.; Müller, M. A.; Müller, S.; Mussa, R.; Nellen, L.; Nguyen, P.; Niculescu-Oglinzanu, M.; Niechciol, Marcus; Nitz, D.; Nosek, D.; Novotný, Vladimír; Nožka, L.; Nucita, A. A.; Núñez, Luis A.; Olinto, Angela V.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Pech, M.; Pedreira, F.; Pękala, Jan; Pelayo, R.; Peña-Rodríguez, Jesús; Pereira, L. A. S.; Perlín, M.; Perrone, L.; Peters, C. F. W.; Petrera, S.; Phuntsok, J.; Pierog, T.; Pimenta, M.; Pirronello, V.; Platino, M.; Poh, J.; Pont, Bjarni; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Puyleart, Andrew; Querchfeld, S.; Quinn, S.; Ramos-Pollán, Raúl; Rautenberg, J.; Ravignani, D.; Reininghaus, Maximilian; Řídký, J.; Riehn, Felix; Risse, M.; Ristori, P.; Rizi, V.; Carvalho, W. Rodrigues de; Rojo, Juan; Roncoroni, Matías J.; Roth, M.; Roulet, Esteban; Rovero, A. C.; Ruehl, Philip; Saffi, S. J.; Sǎftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salina, G.; Sánchez, F.; Santos, Eva; Sarazin, F.; Sarmento, R.; Sarmiento-Cano, C.; Sato, R.; Savina, Pierpaolo; Schauer, Markus; Scherini, V.; Schieler, H.; Schimassek, Martin; Schimp, Michael; Schmidt, D.; Scholten, Olaf; Schovánek, Petr; Schröder, Frank G.; Schröder, S.; Schumacher, J.; Sciutto, S. J.; Shellard, R. C.; Sigl, Guenter; Silli, Gaia; Sima, O.; Šmída, R.; Snow, G. R.; Sommers, P.; Soriano, Jorge F.; Souchard, Julien; Squartini, R.; Stanca, Denis; Stanič, S.; Stasielak, J.; Stassi, P.; Stolpovskiy, M.; Streich, Alexander; Suárez, F.; Suárez-Durán, Mauricio; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Šupík, J.; Szadkowski, Z.; Taboada, A.; Taborda, O. A.; Tapia, A.; Timmermans, C.; Peixoto, C. J. Todero; Tomé, B.; Elipe, G. Torralba; Trávničék, P.; Trini, M.; Tueros, M.; Ulrich, R.; Unger, Michael; Urban, M.; Galicia, J. F. Valdés; Valiño, I.; Valore, L.; Bodegom, Peter M. van; Berg, A. M. van den; Vliet, A. van; Varela, E.; Cárdenas, B. Vargas; Vázquez, R. A.; Veberič, D.; Ventura, Cynthia; Quispe, Indira D. Vergara; Verzi, V.; Vícha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Watson, Alan; Weber, M.; Weindl, A.; Wiedeński, M.; Wiencke, L.; Wilczyński, H.; Wirtz, Marcus; Wittkowski, David; Wundheiler, B.; Yang, Lili; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zehrer, Lukas; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.

doi:10.3847/1538-4357/aae689

Cited by 117 publications

(115 citation statements)

References 37 publications

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“…The large exposure cumulated by these two arrays over the years is nonetheless starting to enable a glimpse at preferred directions beyond the ankle of the cosmic-ray spectrum, which may just be the tip of the iceberg. At E Auger > 8 EeV, the Pierre Auger Collaboration reported the detection of a large-angular scale modulation of the cosmic-ray event rate in right ascension, with a small but significant (> 5 σ) amplitude of 4.7 ± 0.8 % * e-mail: biteau(at)ipno.in2p3.fr [1,2]. At energies where the cosmic-ray (CR) flux is suppressed, E TA > 57 EeV, the Telescope Array Collaboration reported an indication (> 3 σ) of clustering of events on an intermediate angular scale of 20 • [3].…”

Section: The Quest For Anisotropies At Ultra-high Energiesmentioning

confidence: 99%

Covering the celestial sphere at ultra-high energies: Full-sky cosmic-ray maps beyond the ankle and the flux suppression

et al. 2019

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Despite deflections by Galactic and extragalactic magnetic fields, the distribution of ultra-high energy cosmic rays (UHECRs) over the celestial sphere remains a most promising observable for the identification of their sources. Thanks to a large number of detected events over the past years, a large-scale anisotropy at energies above 8 EeV has been identified, and there are also indications from the Telescope Array and Pierre Auger Collaborations of deviations from isotropy at intermediate angular scales (about 20 degrees) at the highest energies. In this contribution, we map the flux of UHECRs over the full sky at energies beyond each of two major features in the UHECR spectrum -the ankle and the flux suppression -, and we derive limits for anisotropy on different angular scales in the two energy regimes. In particular, full-sky coverage enables constraints on low-order multipole moments without assumptions about the strength of higher-order multipoles. Following previous efforts from the two Collaborations, we build full-sky maps accounting for the relative exposure of the arrays and differences in the energy normalizations. The procedure relies on cross-calibrating the UHECR fluxes reconstructed in the declination band around the celestial equator covered by both observatories. We present full-sky maps at energies above ∼ 10 EeV and ∼ 50 EeV, using the largest datasets shared across UHECR collaborations to date. We report on anisotropy searches exploiting full-sky coverage and discuss possible constraints on the distribution of UHECR sources.

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Section: The Quest For Anisotropies At Ultra-high Energiesmentioning

confidence: 99%

Covering the celestial sphere at ultra-high energies: Full-sky cosmic-ray maps beyond the ankle and the flux suppression

et al. 2019

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“…Note that Ultra-High Energy Cosmic Rays (UHECRs) above 1 EeV have a predominant extragalactic origin component (e.g., Abreu et al 2013;Aab et al 2018), in which the energy range of 10 18 − 10 18.5 eV is dominated by protons (Abbasi et al 2017;Schröder et al 2019), and AGNs, especially blazars, may be the candidates of UHECR origin. The escape time and the synchrotron cooling time of the high energy protons (Aharonian 2002)…”

Section: Discussionmentioning

confidence: 99%

Leptonic or Hadronic Emission: The X-Ray Radiation Mechanism of Large-scale Jet Knots in 3C 273

Wang

Zhang

Sun

et al. 2020

ApJ

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A comprehensively theoretical analysis on the broadband spectral energy distributions (SEDs) of large-scale jet knots in 3C 273 is presented for revealing their X-ray radiation mechanism. We show that these SEDs cannot be explained with a single electron population model when the Doppler boosting effect is either considered or not. By adding a more energetic electron (the leptonic model) or proton (the hadronic model) population, the SEDs of all knots are well represented. In the leptonic model, the electron population that contributes the X-ray emission is more energetic than the one responsible for the radio-optical emission by almost two orders of magnitude; the derived equipartition magnetic field strengths (B eq ) are ∼ 0.1 mG. In the hadronic model, the protons with energy of ∼ 20 PeV are required to interpret the observed X-rays; the B eq values are several mG, larger than that in the leptonic model. Based on the fact that no resolved substructures are observed in these knots and the fast cooling-time of the high-energy electrons is difficult to explain the observed X-ray morphologies, we argue that two distinct electron populations accelerated in these knots are unreasonable and their X-ray emission would be attributed to the proton synchrotron radiation accelerated in these knots. In case of these knots have relativistic motion towards the observer, the super-Eddington issue of the hadronic model could be avoided. Multiwavelength polarimetry and the γ-ray observations with high resolution may be helpful to discriminate these models.In this scenario, the synchrotron, SSC, and IC/CMB radiations of a single electron population are used to reproduce the broadband SEDs of knots. The radiating electrons are assumed to have the number distribution as Equation (1). The minimum and maximum energies of electrons are taken as E e,min =1 MeV and E e,max =510 TeV, which are respectively corresponding to γ e ∼ 2 and γ e ∼ 10 9 , where γ e is the Lorenz factor of electrons. In case of the knots do not have the relativistic motions, i.e., δ = Γ = 1, the IC component would be dominated by the SSC process since the energy density of the synchrotron radiation photon field (U syn ) is higher than U ′ CMB . A magnetic field strength (B) lower than the equipartition value (B eq ) is also needed (e.g.

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“…Here, we use the JF12 model again with a coherence length of λ = 60 pc, unless otherwise stated. Further, we use the observed mean logarithm of the mass number ln A [15], and the information on the dipole strength and direction [16] in the following to provide a constrain on this effect for the observed dipole anisotropy. Here, dout,i and (l, b)out,i refer to the resulting dipole features outside our Galaxy using EPOS-LHC (i = 1), Sibyll2.1 (i = 2), and QGSJetII-04 (i = 3).…”

Section: Bias Based On the Auger Datamentioning

confidence: 99%

“…where E obs denotes the observed median energies of the dipole, as given in Table 1, and the mass number A = exp( ln A ). Further, we use the derived power-law behavior of the dipole amplitude [16] d obs = 0.055 (E obs /10 EeV) 0.79 (4.2) and the observed directions (l, b) obs of the dipole -see Table 1. At energies that are not covered by the data of ln A or (l, b) obs we use linear interpolation, where the boundary values are used outside the observed energy range.…”

Section: Total Flux In Case Of the Auger Dipolementioning

confidence: 99%

Galactic magnetic field bias on inferences from UHECR data

Eichmann

Winchen

2020

J. Cosmol. Astropart. Phys.

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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 quadrupole anisotropy, respectively, for the widely-used JF12 magnetic field model. We investigate boundaries on the maximal amplitude of the observed anisotropy and the maximal charge number of UHECRs. Furthermore, the flux modification is discussed in the light of the Auger data on the recent dipole and also the chemical composition. We find that this modification effect yields a modification of the observed flux of up to ∼ 10% for the investigated magnetic field model and the observed dipole, in particular for a heavy chemical composition of UHECRs as suggested by the 'EPOS-LHC' model.

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Large-scale Cosmic-Ray Anisotropies above 4 EeV Measured by the Pierre Auger Observatory

Abstract: We present a detailed study of the large-scale anisotropies of cosmic rays with energies above 4 EeV measured using the Pierre Auger Observatory. For the energy bins [4, 8] EeV and E ≥ 8 EeV, the most

Cited by 117 publications

References 37 publications

Covering the celestial sphere at ultra-high energies: Full-sky cosmic-ray maps beyond the ankle and the flux suppression

Covering the celestial sphere at ultra-high energies: Full-sky cosmic-ray maps beyond the ankle and the flux suppression

Leptonic or Hadronic Emission: The X-Ray Radiation Mechanism of Large-scale Jet Knots in 3C 273

Galactic magnetic field bias on inferences from UHECR data

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