[Paper Review] Weak Gravitational Lensing: Current Status and Future Prospects

Nick Kaiser|arXiv (Cornell University)|Sep 5, 1995

Astronomy and Astrophysical Research3 citations

TL;DR

This paper reviews weak gravitational lensing as a tool for measuring mass distributions in galaxy clusters and on larger cosmological scales, presenting its current status in 1995 and outlining future applications for mapping dark matter. It details how small, coherent distortions in galaxy shapes due to gravitational shear can be statistically analyzed to infer mass maps, with key results showing the technique's feasibility for probing dark matter on supercluster and halo scales.

ABSTRACT

In this review I will describe progress that has been made in determining masses of galaxy clusters using `weak lensing' and how this technique my be applied in the future to determine the dark matter distribution both on supercluster scales and on the scale of galaxy haloes.

Motivation & Objective

• To assess the state of weak gravitational lensing as a method for measuring mass distributions in galaxy clusters in the mid-1990s.
• To evaluate the feasibility of using weak lensing to map dark matter on supercluster scales and within individual galaxy haloes.
• To outline the methodological and observational challenges limiting the technique's application at the time.
• To project future advancements in weak lensing for cosmological mass reconstruction and dark matter mapping.
• To establish a foundation for using statistical shear measurements to infer large-scale mass structures without relying on dynamical assumptions.

Proposed method

• Uses statistical analysis of galaxy shape distortions induced by gravitational shear from intervening mass distributions.
• Applies weak lensing formalism to reconstruct projected mass maps from observed ellipticities of background galaxies.
• Employs a linear shear approximation to relate observed galaxy ellipticity to the convergence and shear of the lensing field.
• Utilizes the shear power spectrum and correlation functions to extract cosmological mass information from large-scale surveys.
• Considers the impact of intrinsic galaxy alignments and observational systematics on mass reconstruction accuracy.
• Proposes future observational strategies using deep imaging and improved photometric redshifts to enhance signal-to-noise.

Experimental results

Research questions

• RQ1 Can weak gravitational lensing reliably measure the mass distribution in galaxy clusters without relying on dynamical assumptions?
• RQ2 What are the systematic errors and limitations in reconstructing mass maps from observed galaxy shape distortions?
• RQ3 How can weak lensing be extended to map dark matter on supercluster scales and within individual galaxy haloes?
• RQ4 What observational strategies are needed to achieve high signal-to-noise in weak lensing measurements?
• RQ5 What are the prospects for using weak lensing to probe the large-scale structure of dark matter in the universe?

Key findings

• Weak gravitational lensing provides a direct, model-independent method for measuring mass distributions in galaxy clusters using only the shapes of background galaxies.
• The technique enables the reconstruction of projected mass maps from statistical shear measurements, even when individual distortions are small and below the noise floor.
• Systematic errors from intrinsic galaxy alignments and observational effects (e.g., seeing, PSF) are identified as major challenges for accurate mass reconstruction.
• The method is shown to be feasible for probing dark matter on scales from galaxy haloes to superclusters, with potential for cosmological parameter constraints.
• Future surveys with deep imaging and improved photometric redshifts are expected to significantly enhance the signal-to-noise of weak lensing measurements.
• The paper establishes that weak lensing is a viable and powerful tool for mapping dark matter on large scales, laying groundwork for future large-scale surveys.