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A search for anisotropy in the arrival directions of ultra high energy cosmic rays recorded at the Pierre Auger Observatory

Published on Apr 30, 2012in Journal of Cosmology and Astroparticle Physics 5.13
· DOI :10.1088/1475-7516/2012/04/040
P. Abreu46
Estimated H-index: 46
(Technical University of Lisbon),
M. Aglietta40
Estimated H-index: 40
(University of Turin)
+ 498 AuthorsMichael Ziolkowski80
Estimated H-index: 80
(Folkwang University of the Arts)
Abstract
Observations of cosmic rays arrival directions made with the Pierre Auger Observatory have previously provided evidence of anisotropy at the 99% CL using the correlation of ultra high energy cosmic rays (UHECRs) with objects drawn from the Veron-Cetty Veron catalog. In this paper we report on the use of three catalog independent methods to search for anisotropy. The 2pt-L, 2pt+ and 3pt methods, each giving a different measure of self-clustering in arrival directions, were tested on mock cosmic ray data sets to study the impacts of sample size and magnetic smearing on their results, accounting for both angular and energy resolutions. If the sources of UHECRs follow the same large scale structure as ordinary galaxies in the local Universe and if UHECRs are deflected no more than a few degrees, a study of mock maps suggests that these three method can efficiently respond to the resulting anisotropy with a P-value = 1.0% or smaller with data sets as few as 100 events. using data taken from January 1, 2004 to July 31, 2010 we examined the 20, 30, ... , 110 highest energy events with a corresponding minimum energy threshold of about 49.3 EeV. The minimum P-values found were 13.5% using the 2pt-L method, 1.0% using the 2pt+ method and 1.1% using the 3pt method for the highest 100 energy events. In view of the multiple (correlated) scans performed on the data set, these catalog-independent methods do not yield strong evidence of anisotropy in the highest energy cosmic rays.
  • References (30)
  • Citations (6)
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References30
Newest
Published on Jun 1, 2013
M. Will24
Estimated H-index: 24
,
L. Wiencke32
Estimated H-index: 32
+ 492 AuthorsA. Weindl32
Estimated H-index: 32
The Pierre Auger Collaboration has reported evidence for anisotropies in the arrival directions of cosmic rays with energies larger thanEth = 55 EeV. There is a correlation above the isotropic expectation with nearby active galaxies and the largest excess is in a celestial region around the position of the radio galaxy Cen A. If these anisotropies are due to nuclei of charge Z, the protons accelerated in those sources are expected, under reasonable assumptions, to lead to excesses in the same re...
309 Citations
Published on Dec 18, 2011in arXiv: High Energy Astrophysical Phenomena
A. Berlind1
Estimated H-index: 1
,
N. Busca1
Estimated H-index: 1
+ 1 AuthorsJ. P. Roberts1
Estimated H-index: 1
We provide realistic mock-catalogs of cosmic rays above 40 EeV, for a pure proton composition, assuming their sources are a random subset of ordinary galaxies in a simulated, volume-limited survey, for various choices of source density: 10^-3.5 Mpc^-3, 10^-4.0 Mpc^-3 and 10^-4.5 Mpc^-3. The spectrum at the source is taken to be E^-2.3 and the effects of cosmological redshifting as well as photo-pion and e^+ e^- energy losses are included.
3 Citations
P. Abreu46
Estimated H-index: 46
,
M. Aglietta40
Estimated H-index: 40
+ 492 AuthorsM. Ziolkowski29
Estimated H-index: 29
Studies of the cosmic ray energy spectrum at the highest energies with the Pierre Auger Observatory
59 Citations
Published on Dec 1, 2010in Astroparticle Physics 3.20
M. Aglietta40
Estimated H-index: 40
(University of Turin),
Denis Allard30
Estimated H-index: 30
(University of Paris)
+ 1 AuthorsJeffrey C. Allen69
Estimated H-index: 69
(New York University)
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, 6 x 10(19) eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1 degrees from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directio...
223 Citations Source Cite
Published on Nov 1, 2009in Journal of Physics G
J. D. Hague13
Estimated H-index: 13
(University of New Mexico),
B. R. Becker16
Estimated H-index: 16
(University of New Mexico)
+ 1 AuthorsJ. A. J. Matthews51
Estimated H-index: 51
(University of New Mexico)
The two-point angular correlation function is a traditional method used to search for deviations from expectations of isotropy. In this paper, we develop and explore a statistically descriptive three-point method with the intended application being the search for deviations from isotropy in the highest energy cosmic rays. We compare the sensitivity of a two-point method and a 'shape–strength' method for a variety of Monte Carlo simulated anisotropic signals. Studies are done with anisotropic sou...
5 Citations Source Cite
Published on Jul 15, 2009in Journal of Cosmology and Astroparticle Physics 5.13
M. Ave16
Estimated H-index: 16
(University of Chicago),
L. Cazon23
Estimated H-index: 23
(University of Chicago)
+ 7 AuthorsT. Venters1
Estimated H-index: 1
(University of Chicago)
We introduce a new method for testing departure from isotropy of points on a sphere based on an enhanced form of the two-point correlation function that we named 2pt+. This method uses information from the two extra variables that define the vector between two points on a sphere. We show that this is a powerful method to test departure from isotropy of a distribution of points on a sphere especially when the number of events is small. We apply the method to a few examples in astronomy and discus...
15 Citations Source Cite
C. Bonifazi1
Estimated H-index: 1
(University of Paris)
We discuss the angular resolution obtained for events registered with the surface detector alone and for hybrid events, i.e., those observed simultaneously by both the surface and fluorescence detectors. The angular accuracy of the surface detector is directly extracted from the data itself and on an event by event basis, and is given as a function of the number of stations triggered by the event and of the zenith angle of the shower. We compare the angular resolution of the surface detector obt...
41 Citations Source Cite
R. Abbasi42
Estimated H-index: 42
,
Charles C. H. Jui1
Estimated H-index: 1
In this paper we investigate the possible existence of multi-point correlation in the arrival direction of the UHECR events detected by the High Resolution Fly's Eye (HiRes) stereo detector. Multi-point correlations could result from the de- flection of UHECRs by galactic and intergalactic magnetic fields, and the subsequent dispersion of arrival directions from point like sources. The search is performed by calculating the solid angle subtended by the polygon between triplets and quadruplets of...
1 Citations
Published on Nov 1, 2008in Astroparticle Physics 3.20
R. Abbasi42
Estimated H-index: 42
(University of Utah),
T. Abu-Zayyad25
Estimated H-index: 25
(University of Utah)
+ 62 AuthorsS. A. Blake19
Estimated H-index: 19
(University of Utah)
Abstract We have searched for correlations between the pointing directions of ultrahigh energy cosmic rays observed by the High Resolution Fly’s Eye experiment and active galactic nuclei (AGN) visible from its northern hemisphere location. No correlations, other than random correlations, have been found. We report our results using search parameters prescribed by the Pierre Auger collaboration. Using these parameters, the Auger collaboration concludes that a positive correlation exists for sourc...
102 Citations Source Cite
Published on Aug 4, 2008in Physical Review Letters 8.84
J. Abraham16
Estimated H-index: 16
,
P. Abreu46
Estimated H-index: 46
+ 454 AuthorsM. Ambrosio31
Estimated H-index: 31
The energy spectrum of cosmic rays above 2.5 x 10{sup 18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index {gamma} of the particle flux, J {proportional_to} E{sup {gamma}}, at energies between 4 x 10{sup 18} eV and 4 x 10{sup 19} eV is 2.69 {+-} 0.02(stat){+-}0.06(syst), steepening to 4.2 {+-} 0.4(stat){+-}0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations....
394 Citations Source Cite
Cited By6
Newest
Published on Jul 18, 2016in Proceedings of SPIE
Paolo Soffitta42
Estimated H-index: 42
,
R. Bellazzini89
Estimated H-index: 89
(University of Pisa)
+ 418 AuthorsRene W. Goosmann14
Estimated H-index: 14
(University of Strasbourg)
XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially- resolved X-ray polarimetry as a breakthrough in ...
145 Citations Source Cite
Published on Jun 1, 2015in European Physical Journal C 5.17
A. Aab19
Estimated H-index: 19
(Folkwang University of the Arts),
P. Abreu46
Estimated H-index: 46
(University of Lisbon)
+ 483 AuthorsA. Almela19
Estimated H-index: 19
(National Scientific and Technical Research Council)
Energy-dependent patterns in the arrival directions of cosmic rays are searched for using data of the Pierre Auger Observatory. We investigate local regions around the highest-energy cosmic rays with E >= 6 x 10(19) eV by analyzing cosmic rays with energies above E >= 5 x 10(18) eV arriving within an angular separation of approximately 15 degrees. We characterize the energy distributions inside these regions by two independent methods, one searching for angular dependence of energy-energy correl...
1 Citations Source Cite
Published on Sep 21, 2014in Classical and Quantum Gravity 3.28
Ilya L. Shapiro28
Estimated H-index: 28
(Tomsk State Pedagogical University),
Poliane M. Teixeira3
Estimated H-index: 3
The Holst term represents an interesting addition to the Einstein–Cartan theory of gravity with torsion. When this term is present the contact interactions between vector and axial vector fermion currents gain an extra parity-violating component. We re-derive this interaction using a simple representation for the Holst term. The same representation serves as a useful basis for the calculation of one-loop divergences in the theory with external fermionic currents and cosmological constant. Furthe...
6 Citations Source Cite
Published on Jan 1, 2014
L. Gonzalez-Mestres1
Estimated H-index: 1
(University of Savoy)
Detailed analyses of WMAP and Planck data can have significant implications for noncyclic pre-Big Bang approaches incorporating a new fundamental scale beyond the Planck scale and, potentially, new ultimate constituents of matter with unconventional basic properties as compared to standard particles. Cosmic-ray experiments at the highest energies can also yield relevant information. Hopefully, future studies will be able to deal with alternatives: i) to standard physics for the structure of the ...
6 Citations Source Cite
Published on Jan 1, 2014
Luis Gonzalez-Mestres11
Estimated H-index: 11
(University of Savoy)
With the present understanding of data, the observed flux suppression for ultra-high energy cosmic rays (UHECR) at energies above 4.10E19 eV can be a signature of the Greisen-Zatsepin-Kuzmin (GZK) cutoff or be related to a similar mechanism. But it may also correspond, for instance, to the maximum energies available at the relevant sources. In both cases, violations of special relativity modifying cosmic-ray propagation or acceleration at very high energy can potentially play a role. Other viola...
12 Citations Source Cite
Published on Dec 1, 2013in Experimental Astronomy 1.35
Paolo Soffitta42
Estimated H-index: 42
(INAF),
Xavier Barcons37
Estimated H-index: 37
(Spanish National Research Council)
+ 96 AuthorsMark Pearce25
Estimated H-index: 25
(Royal Institute of Technology)
X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and temporal variability measurements and to imaging, allows a wealth of physical phenomena in astrophysics to be studied. X-ra ...
64 Citations Source Cite