3D cosmic shear: cosmology from CFHTLenS

Abstract

This paper presents the first application of 3D cosmic shear to a wide-field weak lensing survey. 3D cosmic shear is a technique that analyses weak lensing in three dimensions using a spherical harmonic approach, and does not bin data in the redshift direction. This is applied to CFHTLenS, a 154 square degree imaging survey with a median redshift of 0.7 and an effective number density of 11 galaxies per square arcminute usable for weak lensing. To account for survey masks we apply a 3D pseudo-C ℓ approach on weak lensing data, and to avoid uncertainties in the highly non-linear regime, we separately analyse radial wavenumbers k ≤ 1.5h Mpc −1 and k ≤ 5.0h Mpc −1 , and angular wavenumbers ℓ ≈ 400-5000. We show how one can recover 2D and tomographic power spectra from the full 3D cosmic shear power spectra and present a measurement of the 2D cosmic shear power spectrum, and measurements of a set of 2-bin and 6-bin cosmic shear tomographic power spectra; in doing so we find that using the 3D power in the calculation of such 2D and tomographic power spectra from data naturally accounts for a minimum scale in the matter power spectrum. We use 3D cosmic shear to constrain cosmologies with parameters Ω M , Ω B , σ 8 , h, n s , w 0 , w a . For a non-evolving dark energy equation of state, and assuming a flat cosmology, lensing combined with WMAP7 results in h = 0.78 ± 0.12, Ω M = 0.252 ± 0.079, σ 8 = 0.88 ± 0.23 and w = −1.16 ± 0.38 using only scales k ≤ 1.5h Mpc −1 . We also present results of lensing combined with first year Planck results, where we find no tension with the results from this analysis, but we also find no significant improvement over the Planck results alone. We find evidence of a suppression of power compared to LCDM on small scales 1.5 < k ≤ 5.0h Mpc −1 in the lensing data, which is consistent with predictions of the effect of baryonic feedback on the matter power spectrum.

Cosmological constraints from weak lensing peak statistics with Canada-France-Hawaii Telescope Stripe 82 Survey

“…The best-fit results and the marginalised 1-d mean for Ω m and σ 8 are shown in Table 2. It is seen that similar to weak lensing correlation analyses (e.g., Kilbinger et al 2013;Fu et al 2014;Kitching et al 2014), the constraints on the two parameters from weak lensing peak abundances alone are strongly degenerate. Considering the relation defined by Σ 8 = σ 8 (Ω m /0.27) α and using the same estimation method as in Fu et al (2014), we obtain Σ 8 = 0.82 ± 0.04 and α = 0.43 ± 0.02 and Σ 8 = 0.82 ± 0.03 and α = 0.42 ± 0.02 for the two binning cases, respectively.…”

“…Such effects, namely weak lensing effects, are closely related to the formation and evolution of foreground structures and the global expansion history of the Universe, and therefore are known to be one of the most promising probes in cosmological studies (e.g., Albrecht et al 2006;Abate et al 2012;Amendola et al 2013;Weinberg et al 2013). The cosmic shear two-point (2-pt) correlation analysis has been demonstrated to be a powerful statistics in extracting weak lensing signals from shape measurements of background galaxies (e.g., Fu et al 2008;Heymans et al 2012;Kilbinger et al 2013;Jee et al 2013;Kitching et al 2014). On the other hand, 2-pt correlations can only reveal part of the cosmological information embedded in weak lensing signals given the nonlinearity of the structure formation.…”

SKA weak lensing – III. Added value of multiwavelength synergies for the mitigation of systematics

“…Recently, several analyses have tried to asses the impact of such systematics on state-of-the-art cosmic shear surveys such as the CFHTLenS (see e.g. Kitching et al 2014;Ade et al 2015). Since the non-linear evolution of density fluctuations affects mostly the smaller (angular) scales, the simplest way to avoid having to deal with non-linear perturbations is therefore to limit the analysis to large cosmic scales.…”

“…8. This gives us a proxy for the fraction of information coming from non-linear scales, which have to be treated more carefully because the poorly understood effect of baryons and, in general, the non-linear growth of structures demands some degree of ad hoc modelling (Semboloni et al 2013;Kitching et al 2014;Fedeli et al 2014;Fedeli 2014). What this plot tells us is that, in the fixed multipole range 20 ℓ 3000, the total SNR for the cosmic shear angular power spectrum in a given redshift bin pair is ∆ ij nl times what we would get if all the scales considered were linear.…”

On scale-dependent cosmic shear systematic effects

“…Supplementing cosmic shear information with redshift information of galaxies is known as 3D cosmic shear (see Kitching et al 2014, and references therein for an exposition). Cosmic shear 'tomography' is an approximation of 3D cosmic shear by assuming a fixed linear relation between the radial and azimuthal wavenumbers for the 3D shear field (the Limber approximation), and a binning in redshift (Kitching, Heavens & Miller 2011).…”