Calibration biases in measurements of weak lensing

• Verfasst von: Bartelmann, Matthias [VerfasserIn]
• Verfasst von: Viola, Massimo [VerfasserIn]
• Verfasst von: Melchior, Peter [VerfasserIn]
• Verfasst von: Schäfer, Björn Malte [VerfasserIn]
• Titel: Calibration biases in measurements of weak lensing
• Verf.angabe: Matthias Bartelmann, Massimo Viola, Peter Melchior, Björn M. Schäfer
• Fussnoten: Gesehen am 21.09.2017
• Titel Quelle: Enthalten in: De.arxiv.org
• Jahr Quelle: 2011
• Band/Heft Quelle: (2011) Artikel-Nummer 1103.5923, 5Seiten
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1563691310

Abstract

As recently shown by Viola et al., the common (KSB) method for measuring weak gravitational shear creates a non-linear relation between the measured and the true shear 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 Omega_matter and sigma_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 measured. 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.