Magnification effects as measures of large-scale structure

Abstract

The magnification effects of clustered matter produce variations in the image sizes and number density of galaxies across the sky. This paper advocates the use of these effects in wide field surveys to map large-scale structure and the profiles of galaxy and cluster sized halos. The magnitude of the size variation as a function of angular scale is computed and the signal-to-noise is estimated for different survey parameters. Forthcoming surveys, especially well designed space-based imaging surveys, will have high signal-to-noise on scales of about 0.1 arcminute to several degrees. Thus the clustering of matter could be measured on spatial scales of about 50 Kpc to 100 Mpc. The signal-to-noise is dominated by sample variance rather than shot-noise due to the finite number density of galaxies, hence the accuracy of the measurements will be limited primarily by survey area, sampling strategy and possible systematics. Methods based on magnification are compared with the use of shape distortions and the contrasts and complementarities are discussed. Future work needed to plan survey strategy and interpret measurements based on magnification is outlined.