— Luminous tracers have been used extensively to map the large-scale matter distribution in the Universe. Similarly the dynamics of stars or galaxies can be used to estimate masses of galaxies and clusters of galaxies. However, assumptions need to be made about the dynamical state or how well galaxies trace the underlying dark matter distribution. The… CONTINUE READING
Fig. 4. – Left panel: Plot of the apparent magnitude versus half-light radius for RCS data from . The rectangle indicates the sample of stars that can be used to model the PSF variation. Brighter stars saturate and their observed sizes increase as can be seen as well. Right panel: An example of the pattern of PSF anisotropy for MegaCam on CFHT from . The sticks indicate the direction of the major axis of the PSF and the length is proportional to the PSF ellipticity. A coherent pattern across the field-of-view is clearly visible.