Power Spectra for Galaxy Shape Correlations

Abstract

It has recently been argued that the observed ellipticities of galaxies may be determined at least in part by the primordial tidal gravitational field in which the galaxy formed. Long-range correlations in the tidal field could thus lead to an ellipticity-ellipticity correlation for widely separated galaxies. I present results of a calculation of the angular power spectrum of intrinsic galaxy shape correlations using a new model relating ellipticity to angular momentum. I show that for low redshift galaxy surveys, the model predicts that intrinsic correlations will dominate correlations induced by weak lensing, in good agreement with previous theoretical work and observations. The model also produces `E-mode' correlations enhanced by a factor of 3.5 over `B-modes' on small scales, making it harder to disentangle intrinsic correlations from weak lensing.Comment: 4 pages, 1 figure. in ``The Shapes of Galaxies and Their Dark Halos,'' Yale Cosmology Workshop, Ed. P. Natarajan (New Haven CT, May 2001). Revised web version corrects lensing curve normalisation in fig.1; text as publishe