Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter

Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{$6\times 10^{19}$eV}. The anisotropy was measured by the fraction of arrival directions that are less than $3.1^\circ$ from the position of an active galactic nucleus within 75 Mpc (using the V\'eron-Cetty and V\'eron $12^{\rm th}$ catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is $(38^{+7}_{-6})$, compared with $21$ expected for isotropic cosmic rays. This is down from the early estimate of $(69^{+11}_{-13})$. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201

Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory

The advent of the Auger Engineering Radio Array (AERA) necessitates the development of a powerful framework for the analysis of radio measurements of cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air shower radio emission in coincidence with the surface particle detectors and fluorescence telescopes of the Pierre Auger Observatory, the radio analysis functionality had to be incorporated in the existing hybrid analysis solutions for fluoresence and surface detector data. This goal has been achieved in a natural way by extending the existing Auger Offline software framework with radio functionality. In this article, we lay out the design, highlights and features of the radio extension implemented in the Auger Offline framework. Its functionality has achieved a high degree of sophistication and offers advanced features such as vectorial reconstruction of the electric field, advanced signal processing algorithms, a transparent and efficient handling of FFTs, a very detailed simulation of detector effects, and the read-in of multiple data formats including data from various radio simulation codes. The source code of this radio functionality can be made available to interested parties on request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to author list and references in v

Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory

We present the results of searches for dipolar-type anisotropies in different energy ranges above $2.5\times 10^{17}$ eV with the surface detector array of the Pierre Auger Observatory, reporting on both the phase and the amplitude measurements of the first harmonic modulation in the right-ascension distribution. Upper limits on the amplitudes are obtained, which provide the most stringent bounds at present, being below 2% at 99% $C.L.$ for EeV energies. We also compare our results to those of previous experiments as well as with some theoretical expectations.Comment: 28 pages, 11 figure

Depth Of Maximum Of Air-shower Profiles At The Pierre Auger Observatory. I. Measurements At Energies Above 1017.8ev

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Atmospheric Radiation Monitor

The Atmospheric Radiation Monitor (MonRAt) is a compact experiment aiming to measure the fluorescence radiation in the atmosphere initiated by cosmic rays with energies between 100 PeV and 100 EeV. It is composite by a mirror focusing on a multianodic photomultiplier with an ultraviolet filter - selecting photons with wavelengths between 300 and 450 nm - And the data acquisition boards. The monitor is intended to contribute in problems such as the study of fluorescence radiation yield in the atmosphere parameterized with atmospheric conditions.Hara, T., (1970) Acta Phys. Acad. Sci. Hung., 29 (SUPPL. 3), p. 361Baltrusaitus, R.M., (1985) Nucl. Instr. and Meth. in Phys. Res., A240, p. 410Abu-Zayyad, T., (2000) Nucl. Instr. and Meth. in Phys. Res., A450, p. 253Abraham, J., (2004) Nucl. Instr. and Meth. in Phys. Res., A523, p. 50Fukushima, M., (2003) Prog. Theo. Phys. Suppl., 151, p. 206Scarsi, L., (2001) Proc. 27th Int. Cosmic Ray Conf., p. 839. , HamburgStecker, F.W., (2004) Nucl. Phys., B139, p. 433Bunner, A.N., (1967) Cosmic Ray Detection by Atmospheric Fluorescence, , PhD Thesis, Cornell Univ. (FebDavidson, G., O'Neil, R., (1964) J. Chem. Phys., 41, p. 3946Kakimoto, K., (1996) Nucl. Instr. and Meth. in Phys. Res., A372, p. 527Nagano, M., (2003) Astropart. Phys., 20, p. 293Nagano, M., (2004) Astropart. Phys., 22, p. 235Beltz, J.W., (2006) Astropart. Phys., 25, p. 129P. Collin et al. astroph/06121110De Souza, V., Medina-Tanco, G., Ortiz, J.A., (2006) Astropart. Phys., 25, p. 129Leigui De Oliveira, M.A., (2008) Monitor de Radiacao Atmosferica, , XXIX ENFPC, SBF, Sao Lourenco, BrazilHamamatsu Photonics K.K., , http://www.hamamatsu.comHeck, D., Knapp, J., Capdevielle, J.N., Schatz, G., Thouw, T., (1998) Report FZKA 6019, , http://www-ik.fzk.de/heck/publications/fzka6019.pdfFletcher, R.S., (1994) Phys. Rev. D, D50, p. 5710(2001) IPCC Report, , http://www.ipcc.chLeigui De Oliveira, M.A., Peixoto, C.J.T., Leao, M.S.A.B., The ionization energy deposit in the atmosphere and the fluorescence light generation at shower axis (2009) 31stICRC, , Lodz, Session: HE.1.4 . ID=98Flowers, E.C., McCormick, R.A., Kurfis, J., (1969) J. Appl. Meteorology, 8, p. 955Sokolsky, P., (1996) Proc. of Int. Sym. on EHECRs: Astrophysics and Future Observatories, p. 253. , Ed. M. Nagan

Muons In Air Showers At The Pierre Auger Observatory: Mean Number In Highly Inclined Events

We present the first hybrid measurement of the average muon number in air showers at ultrahigh energies, initiated by cosmic rays with zenith angles between 62\ub0 and 80\ub0. The measurement is based on 174 hybrid events recorded simultaneously with the surface detector array and the fluorescence detector of the Pierre Auger Observatory. The muon number for each shower is derived by scaling a simulated reference profile of the lateral muon density distribution at the ground until it fits the data. A 10^19\u2009\u2009eV shower with a zenith angle of 67\ub0, which arrives at the surface detector array at an altitude of 1450 m above sea level, contains on average (2.68\ub10.04\ub10.48(sys)) 710^7 muons with energies larger than 0.3 GeV. The logarithmic gain dlnN\u3bc/dlnE of muons with increasing energy between 4 710^18\u2009\u2009eV and 5 710^19\u2009\u2009eV is measured to be (1.029\ub10.024\ub10.030(sys))

Reconstruction Of Inclined Air Showers Detected With The Pierre Auger Observatory

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Search for signatures of magnetically-induced alignment in the arrival directions measured by the Pierre Auger Observatory

International audienceWe present the results of an analysis of data recorded at the Pierre Auger Observatory in which we search for groups of directionally-aligned events (or 'multiplets') which exhibit a correlation between arrival direction and the inverse of the energy. These signatures are expected from sets of events coming from the same source after having been deflected by intervening coherent magnetic fields. The observation of several events from the same source would open the possibility to accurately reconstruct the position of the source and also measure the integral of the component of the magnetic field orthogonal to the trajectory of the cosmic rays. We describe the largest multiplets found and compute the probability that they appeared by chance from an isotropic distribution. We find no statistically significant evidence for the presence of multiplets arising from magnetic deflections in the present data

Anisotropy and chemical compositionof ultra-high energy cosmic rays usingarrival directions measured by thePierre Auger Observatory

The Pierre Auger Collaboration has reported evidence for anisotropy in the dis- tribution of arrival directions of the cosmic rays with energies E > Eth = 5.5×10^19 eV. These show a correlation with the distribution of nearby extragalactic objects, including an appar- ent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > Eth are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above Eth/Z (for illustrative values of Z = 6, 13, 26). If the anisotropies above Eth are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies

Depth Of Maximum Of Air-shower Profiles At The Pierre Auger Observatory. Ii. Composition Implications

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