Cosmic variance

in weak gravitational lensing

In this work, we highlight the shortcomings of using a deep narrow sample as a training sample to obtain redshift-dependent shear calibration biases for large surveys. Using COSMOS catalog, which is the largest contiguous survey from the Hubble Space Telescope, we showed that individual redshift bins were dominated by a single (or few) overdensities and voids. Thus, they cannot be used to obtain the redshift-dependent calibration for shear estimates since the sample is dominanted by local environment and is not a representative sample of the Universe. We tried a few possible techniques to mitigate this effect, but nonetheless, the environment effects were too strong to obtain a useful training sample from COSMOS.

Papers that have come out of this project:

  1. The impact of cosmic variance on simulating weak lensing surveys
    A. Kannawadi, R. Mandelbaum, C. Lackner (2015) MNRAS 449 (4), 3597-3612
  2. The third gravitational lensing accuracy testing (GREAT3) challenge handbook
    R. Mandelbaum, B. Rowe, J. Bosch, C. Chang, F. Courbin, M. Gill, M. Jarvis, A. Kannawadi, T. Kacprzak, C. Lackner, A. Leauthaud, H. Miyatake, R. Nakajima, J. Rhodes, M. Simet, J. Zuntz, B. Armstrong, S. Bridle, J. Coupon, J. P. Dietrich, M. Gentile, C. Heymans, A. S. Jurling, S. M. Kent, D. Kirkby, D. Margala, R. Massey, P. Melchior, J. Peterson, A. Roodman, T. Schrabback (2014) ApJS, 212 (1), 5