A Detection of Weak Lensing Magnification using Galaxy Sizes and Magnitudes

TL;DR

This paper introduces a novel method to detect weak lensing magnification by analyzing galaxy sizes and magnitudes, providing an independent approach that complements traditional shear measurements.

Contribution

It presents the first detection of weak lensing magnification using galaxy sizes and magnitudes, demonstrating its feasibility with data from the COSMOS survey.

Findings

Detection of weak lensing magnification consistent with shear measurements

Achieved about 40% of the signal-to-noise ratio of shear-based methods

Discussed systematic challenges and potential of the new technique

Abstract

Weak lensing is commonly measured using shear through galaxy ellipticities, or using the effect of magnification bias on galaxy number densities. Here, we report on the first detection of weak lensing magnification with a new, independent technique using the distribution of galaxy sizes and magnitudes. These data come for free in galaxy surveys designed for measuring shear. We present the magnification estimator and apply it to an X-ray selected sample of galaxy groups in the COSMOS HST survey. The measurement of the projected surface density \Sigma(r) is consistent with the shear measurements within the uncertainties, and has roughly 40% of the signal-to-noise of the latter. We discuss systematic issues and challenges to realizing the potential of this new probe of weak lensing.