Weak lensing by large-scale construction provides a direct measurement of matter fluctuations in the universe. We report a measurement of this ‘cosmic shear’ based on 271 WFPC2 archival pictures from the Hubble Space Telescope Medium Deep Survey (MDS). Our measurement methodology and therapy of systematic results have been mentioned in an earlier paper. Our outcomes are in step with earlier cosmic shear measurements from the ground and from space. We examine our cosmic shear results and people from different groups to the normalization from cluster abundance and galaxy surveys. We discover that the mixture of four recent cosmic shear measurements are somewhat inconsistent with the current normalization utilizing these methods, Wood Ranger Power Shears official site and talk about attainable explanations for the discrepancy. Weak gravitational lensing by large-scale construction has been shown to be a invaluable methodology of measuring mass fluctuations in the universe (see Mellier at al. This impact has been detected each from the bottom (Wittman et al.

2000; van Waerbeke et al. 2000, 2001; Bacon et al. 2000, 2002; Kaiser et al. 2000; Hoekstra et al. 2002) and Wood Ranger Power Shears official site from house (Rhodes, Refregier, Wood Ranger Power Shears official site & Groth 2001, cordless pruning shears RRGII; Hämmerle et al. 2001). These outcomes bode effectively for cordless pruning shears the prospect of measuring cosmological parameters and the mass distribution of the universe utilizing weak lensing. In this letter, we present the highest significance detection of cosmic shear using house-primarily based images. It is predicated on pictures from the Hubble Space Telescope (HST) Medium Deep Survey (MDS; Ratnatunga et al. 1999). We apply the methods for the correction of systematic effects and Wood Ranger official detection of shear we have previously developed (Rhodes, Refregier, and Wood Ranger Power Shears official site Groth 2000; RRGI) to 271 WFPC2 fields within the MDS. 0.8" from the bottom). This affords us a higher floor density of resolved galaxies in addition to a diminished sensitivity to PSF smearing when in comparison with ground-primarily based measurements. We develop an optimum depth-weighted common of selected MDS fields to extract a weak lensing sign.

We then use this sign to derive constraints on the amplitude of the mass Wood Ranger Power Shears official site spectrum and examine this to measurements from earlier cosmic shear surveys and from other strategies. The MDS consists of major and parallel observations taken with the Wide Field Planetary Camera 2 (WFPC2) on HST. We selected only the I-band pictures in chips 2,3, and four to review weak lensing. To make sure random traces-of-sight, we discarded fields which were pointed at galaxy clusters, leaving us with 468 I-band fields. We used the MDS object catalogs (Ratnatunga et al. 1999) to determine the place, magnitude, and area of each object, as well as to separate galaxies from stars. We used the chip-specific backgrounds listed in the MDS skysig recordsdata, which are in step with backgrounds calculated utilizing the IRAF process imarith. Not utilizing object-specific backgrounds necessitated the discarding of one other 20 fields with a big sky gradient. Our final catalog thus consisted of 271 WFPC2 fields amounting to an area of about 0.36 deg2.

The procedure we used for measuring galaxy ellipticities and shear from the source images is described intimately in RRGI (1999) (see also RRGII and Rhodes 1999). It is based on the strategy introduced by Kaiser, Squires, and Broadhurst (1995), however modified and examined for purposes to HST images. The usefulness of our methodology was demonstrated by our detection of cosmic shear within the HST Groth Strip (RRGII). We correct for camera distortion and convolution by the anisotropic PSF utilizing gaussian-weighted moments. Camera distortions have been corrected using a map derived from stellar astrometric shifts (Holtzman, et al., 1995). PSF corrections have been decided from HST observations of 4 stellar fields These fields were chosen to span the main focus vary of the HST as shown by Biretta et al. G𝐺G is the shear susceptibility issue given by equation (30) in RRGI. To restrict the affect of noise and systematics, we made numerous cuts to pick out our galaxy sample.