Calibration biases in measurements of weak lensing

M. Bartelmann, M. Viola, P. Melchior, B. M. Schäfer

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

As shown recently, the common KSB method for measuring weak gravitational shear creates a non-linear relation between the measured and the true ellipticity of objects. We investigate here what effect such a non-linear calibration relation may have on cosmological parameter estimates from weak lensing if a simpler, linear calibration relation is assumed. We show that the non-linear relation introduces a bias in the shear-correlation amplitude and thus a bias in the cosmological parameters Ω m0 and σ 8. Its direction and magnitude depends on whether the point-spread function is narrow or wide compared to the galaxy images from which the shear is estimated. Substantial over-or underestimates of the cosmological parameters are equally possible, depending also on the variant of the KSB method. Our results show that for trustable cosmological-parameter estimates from measurements of weak lensing, one must verify that the method employed is free from ellipticity-dependent biases or monitor that the calibration relation inferred from simulations is applicable to the survey at hand.

Original languageEnglish (US)
Article numberA98
JournalAstronomy and Astrophysics
Volume547
DOIs
StatePublished - 2012

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Cosmological parameters
  • Cosmology: observations
  • Dark matter
  • Large-scale structure of Universe

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