Very weak lensing in the CFHTLS wide: cosmology from cosmic shear in the linear regime

Abstract

Aims. We present an exploration of weak lensing by large-scale structure in the linear regime, using the third-year (T0003) CFHTLS Wide data release. Our results place tight constraints on the scaling of the amplitude of the matter power spectrum σ 8 with the matter density Ω m . Methods. Spanning 57 square degrees to i AB = 24.5 over three independent fields, the unprecedented contiguous area of this survey permits high signal-to-noise measurements of two-point shear statistics from 1 arcmin to 4 degrees. Understanding systematic errors in our analysis is vital in interpreting the results. We therefore demonstrate the percent-level accuracy of our method using STEP simulations, an E/B-mode decomposition of the data, and the star-galaxy cross correlation function. We also present a thorough analysis of the galaxy redshift distribution using redshift data from the CFHTLS T0003 Deep fields that probe the same spatial regions as the Wide fields. Results. We find σ 8 (Ω m /0.25) 0.64 = 0.785 ± 0.043 using the aperture-mass statistic for the full range of angular scales for an assumed flat cosmology, in excellent agreement with WMAP3 constraints. The largest physical scale probed by our analysis is 85 Mpc, assuming a mean redshift of lenses of 0.5 and a ΛCDM cosmology. This allows for the first time to constrain cosmology using only cosmic shear measurements in the linear regime. Using only angular scales θ > 85 arcmin, we find σ 8 (Ω m /0.25) 0.53 lin = 0.837 ± 0.084, which agree with the results from our full analysis. Combining our results with data from WMAP3, we find Ω m = 0.248 ± 0.019 and σ 8 = 0.771 ± 0.029.

Confirmation of the Copernican principle through the anisotropic kinetic Sunyaev Zel'dovich effect

“…We take a minimalist's approach to circumvent this obstacle. The measured matter clustering and its evolution agree with the standard Lambda cold dark matter (LCDM) [29,[38][39][40] to z ∼ 1, so do the galaxy clustering and evolution [41][42][43]. Hence the density inhomogeneities in any viable LTB models must be consistent with the LCDM prediction, within a factor of approximately 2 observational uncertainties.…”

“…Scaling the observed weak lensing r.m.s. convergence k ∼ 10 −2 at approximately 10 arcminute scale [29], the r.m.s. fluctuation in d e projected over Gpc length is 0.1 at the same angular scale.…”

Observational probes of cosmic acceleration

“…Several wide-field optical surveys were ongoing at the time, including the deep 170 deg 2 CFHT Legacy Survey (for which cosmic shear was a key science driver) and the very deep multiwavelength COSMOS survey with high-resolution optical imaging from HST/ACS (Massey et al, 2007b;Schrabback et al, 2010). The CFHTLS presented some early results Semboloni et al, 2006a;Fu et al, 2008), but following this there was a rather bleak period of time.…”

Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS

“…Larger surveys have significantly reduced statistical uncertainties (e.g. Hoekstra et al 2002;Brown et al 2003;Jarvis et al 2003;Van Waerbeke et al 2005;Hoekstra et al 2006;Semboloni et al 2006;Hetterscheidt et al 2007;Fu et al 2008), while tests on simulated data have led to better understanding of PSF systematics (Heymans et al 2006a;Massey et al 2007a;Bridle et al 2010, and references therein). Finally, because it is a geometric effect, gravitational lensing depends on the source redshift distribution, where most earlier measurements have had to rely on external redshift calibrations from the small Hubble Deep Fields.…”