Wednesday, November 16, 2011

1111.3591 (B. Leistedt et al.)

3DEX: a code for Fast Fourier-Bessel Decomposition of Spherical 3D Surveys    [PDF]

B. Leistedt, A. Rassat, A. Refregier, J. -L. Starck
High precision cosmology requires analysis of large scale surveys in 3D spherical coordinates, i.e. Fourier-Bessel decomposition. Current methods are insufficient for future data-sets from wide-field cosmology surveys. The aim of this paper is to present a public code for fast Fourier-Bessel decomposition which can be applied to cosmological data or 3D data in spherical coordinates in other scientific fields. In this paper, we present an equivalent formulation of the Fourier-Bessel decomposition which separates radial and tangential calculations. We propose to make use of existing pixelisation scheme HEALPix for rapid calculation of the tangential modes. 3DEX (3D EXpansions) is a public code for fast Fourier-Bessel decomposition of 3D all-sky surveys which takes advantage of HEALPix for the calculation of tangential modes. We perform tests on very large simulations and we compare precision and computation time of our method with an optimised implementation of the Fourier-Bessel original formulation. For surveys with millions of galaxies, computation time is reduced by a factor 4-12 depending on the desired scales and accuracy. The formulation is also suitable for pre-calculations and external storage of the spherical harmonics, which allows for further speed improvements. The 3DEX code can accommodate data with masked regions of missing data. 3DEX can also be used in other disciplines, where 3D data is to be analysed in spherical coordinates. The code and documentation can be downloaded at http://ixkael.com/blog/3dex.
View original: http://arxiv.org/abs/1111.3591

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