Issue |
A&A
Volume 441, Number 1, October I 2005
|
|
---|---|---|
Page(s) | 407 - 415 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361:20052833 | |
Published online | 13 September 2005 |
Generalised 3D-reconstruction method of a dipole anisotropy in cosmic-ray distributions
Institut de Physique Nucléaire d'Orsay, IN2P3-CNRS/Université Paris-Sud, 91406 Orsay Cedex, France e-mail: parizot@ipno.in2p3.fr
Received:
7
February
2005
Accepted:
5
April
2005
We develop a method for studying the anisotropy of a cosmic-ray angular distribution, using both the right ascension and the declination of the arrival directions. It generalises the full-sky coverage method of Sommers (2001, Astropart. Phys., 14, 271) to partial-sky coverage experiments. When the angular distribution consists of a dipolar modulation of an otherwise isotropic flux, the method allows one to reconstruct the dipole amplitude and the dipole orientation in 3D space. We analyse the statistical properties of the method in detail, introducing the concept of reconstruction power, and show that it is generally more powerful than the standard Rayleigh analysis in right ascension. We clarify the link between the traditionally-used first harmonic amplitude and the true physical dipole amplitude, and we investigate the variation of the reconstruction powers as a function of the dipole orientation. We illustrate the method by computing the amplitude and angular reconstruction powers of the Pierre Auger Observatory, with the Southern site alone and with both Southern and Northern sites. In this particular case, we find that with an additional similar site in the Northern hemisphere the time needed for the method to reveal a significant departure from an isotropic cosmic-ray distribution would be reduced by a factor of about eight.
Key words: ISM: cosmic rays / methods: data analysis / methods: statistical
© ESO, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.