Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-03-08
Mon.Not.Roy.Astron.Soc. 344 (2003) 673
Astronomy and Astrophysics
Astrophysics
13 LaTex pages, including 17 figures, submitted to MNRAS. Includes updated figures 1 & 14, added references, and minor correct
Scientific paper
10.1046/j.1365-8711.2003.06877.x
The recent measurements of weak lensing by large-scale structure present significant new opportunities for studies of the matter distribution in the universe. Here, we present a new cosmic shear survey carried out with the Echelle Spectrograph and Imager on the Keck II telescope. This covers a total of 0.6 square degrees in 173 fields probing independent lines of sight, hence minimising the impact of sample variance. We also extend our measurements of cosmic shear with the William Herschel Telescope (Bacon, Refregier & Ellis 2000) to a survey area of 1 square degree. The joint measurements with two independent telescopes allow us to assess the impact of instrument-specific systematics, one of the major difficulties in cosmic shear measurements. For both surveys, we carefully account for effects such as smearing by the point spread function and shearing due to telescope optics. We find negligible residuals in both cases and recover mutually consistent cosmic shear signals, significant at the 5.1 sigma level. We present a simple method to compute the statistical error in the shear correlation function, including non-gaussian sample variance and the covariance between different angular bins. We measure shear correlation functions for all fields and use these to ascertain the amplitude of the matter power spectrum, finding sigma_8 (Omega_m/0.3)^0.68 = 0.97 \pm 0.13 with 0.14
Bacon David
Ellis Richard
Massey Richard
Refregier Alexandre
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