Wideangle effects on galaxy ellipticity correlations
Abstract
We show an efficient way to compute wideangle or allsky statistics of galaxy intrinsic alignment in threedimensional configuration space. For this purpose, we expand the twopoint correlation function using a newly introduced spindependent tripolar spherical harmonic basis. Therefore, the angular dependencies on the two line of sight (LOS) directions pointing to each pair of objects, which are degenerate with each other in the conventional analysis under the smallangle or planeparallel (PP) approximation, are unambiguously decomposed. By means of this, we, for the first time, compute the wideangle auto and cross correlations between intrinsic ellipticities, number densities, and velocities of galaxies and compare them with the PPlimit results. For the ellipticityellipticity and densityellipticity correlations, we find more than $10{{\ \rm per\ cent}}$ deviation from the PPlimit results if the opening angle between two LOS directions exceeds 30°50°. It is also shown that even if the PPlimit result is strictly zero, the nonvanishing correlation is obtained over the various scales, arising purely from the curvedsky effects. Our results indicate the importance of the data analysis not relying on the PP approximation in order to determine the cosmological parameters more precisely and/or find new physics via ongoing and forthcoming wideangle galaxy surveys.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 May 2021
 DOI:
 10.1093/mnrasl/slab009
 arXiv:
 arXiv:2012.13290
 Bibcode:
 2021MNRAS.503L...6S
 Keywords:

 gravitational lensing: weak;
 cosmology: observations;
 cosmology: theory;
 dark energy;
 dark matter;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 5 pages, 2 figures