Searches for large-scale anisotropy in the arrival directions of cosmic rays detected above energy of 1019 eV at the Pierre auger observatory and the telescope array

The Pierre Auger Collaboration, The Telescope Array Collaboration, G. Farrar

Research output: Contribution to journalArticle

Abstract

Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above 1019 eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above 1019 eV. No significant deviation from isotropic expectations is found throughout the analyses performed. Upper limits on the amplitudes of the dipole and quadrupole moments are derived as a function of the direction in the sky, varying between 7% and 13% for the dipole and between 7% and 10% for a symmetric quadrupole.

Original languageEnglish (US)
Article number794
JournalAstrophysical Journal
Volume794
Issue number2
DOIs
StatePublished - Oct 20 2014

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cosmic ray
arrivals
cosmic rays
observatories
anisotropy
observatory
spherical harmonics
telescopes
sky
quadrupoles
moments
energy
Southern Hemisphere
Northern Hemisphere
power spectra
dipole moments
dipoles
deviation
expansion
coefficients

Keywords

  • Astroparticle physics
  • Cosmic rays

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Searches for large-scale anisotropy in the arrival directions of cosmic rays detected above energy of 1019 eV at the Pierre auger observatory and the telescope array. / The Pierre Auger Collaboration; The Telescope Array Collaboration; Farrar, G.

In: Astrophysical Journal, Vol. 794, No. 2, 794, 20.10.2014.

Research output: Contribution to journalArticle

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abstract = "Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above 1019 eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above 1019 eV. No significant deviation from isotropic expectations is found throughout the analyses performed. Upper limits on the amplitudes of the dipole and quadrupole moments are derived as a function of the direction in the sky, varying between 7{\%} and 13{\%} for the dipole and between 7{\%} and 10{\%} for a symmetric quadrupole.",
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