3D weak lensing

Abstract

I propose an analysis method, based on spin-spherical harmonics and spherical Bessel functions, for large-scale weak lensing surveys which have source distance information through photometric redshifts. I show that the distance information can significantly reduce statistical errors on cosmological parameters; in particular, 3D lensing analysis offers excellent prospects for constraining the equation of state of the vacuum energy which dominates the energy density of the Universe. I show that the ratio of pressure to energy density could be determined to an accuracy of $\sim 1%$ or better. Having distance information also offers significant advantages in the control of systematic effects such as the intrinsic alignment of galaxies. The case for obtaining photometric redshifts is therefore compelling. A signal-to-noise eigenmode analysis of the modes shows that the modes with highest signal-to-noise correspond quite closely to ignoring the redshift information, but there is significant extra information from a few radial modes. These modes are generally long-wavelength, suggesting that useful information can be gleaned even if the photometric redshifts are relatively inaccurate.

8 pages; submitted to MNRAS