A catalogue of 62 million galaxy shapes from 3500 sq deg of UNIONS r-band imaging achieves an effective source density of 4.96 arcmin^{-2} and shape noise of 0.27 after PSF calibration and validation.
Mapping the Dark Matter in Clusters
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abstract
Massive clusters of galaxies gravitationally shear the images of faint background galaxies. At large impact parameters the shear is weak, but can still be measured, to a reasonable degree of significance, as a statistical anisotropy of the faint galaxy images. We describe techniques for measuring the shear and discuss the interpretation of the shear field. We have applied this analysis to ms1224+007. We find a clear detection of the shear, but, puzzlingly, we find a mass about three times that obtained by application of the virial theorem, and obtain a very large mass-to-light ratio. Similar results have been obtained by other groups, and we discuss their implications.
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UNIONS-3500 Weak Lensing: I. A Galaxy Shape Catalogue in the Northern Sky
A catalogue of 62 million galaxy shapes from 3500 sq deg of UNIONS r-band imaging achieves an effective source density of 4.96 arcmin^{-2} and shape noise of 0.27 after PSF calibration and validation.