[Paper Review] Quasar Lensing

F. Courbin, Prasenjit Saha+1 more|arXiv (Cornell University)|Aug 1, 2002

Adaptive optics and wavefront sensing4 citations

TL;DR

This paper reviews strong gravitational lensing by massive structures, focusing on quasars as background sources. It explains how multiple lensed images and time-delays enable precise measurements of the Hubble parameter H₀, with recent advances including microlensing effects from stars in the lensing galaxy.

ABSTRACT

Massive structures, such as galaxies, act as strong gravitational lenses on background sources. When the background source is a quasar, several lensed images are seen, as magnified or de-magnified versions of the same object. The detailed study of the image configuration and the measurement of ``time-delays'' between the images yield estimates of the Hubble parameter H_0. We describe in a simple way the phenomenon of strong lensing and review recent progress made in the field, including microlensing by stars in the main lensing galaxy.

Motivation & Objective

• To explain the physical mechanism of strong gravitational lensing in the context of quasars as background sources.
• To review recent progress in measuring the Hubble parameter H₀ using time-delay observations between multiple lensed images.
• To examine the role of microlensing by stars within the main lensing galaxy in shaping observed image configurations.
• To provide a simplified yet comprehensive overview of quasar lensing phenomena for researchers in cosmology and astrophysics.

Proposed method

• Utilizes the principles of general relativity to model how massive galaxies bend light from distant quasars, creating multiple images.
• Analyzes time-delay measurements between multiple images of the same quasar to constrain the Hubble parameter H₀.
• Incorporates microlensing effects from stars in the main lensing galaxy to refine image magnification and configuration predictions.
• Reviews observational data and theoretical models to assess consistency with cosmological distance measurements.
• Applies lensing geometry and time-delay analysis to estimate H₀ with improved precision.

Experimental results

Research questions

• RQ1 How do strong gravitational lensing effects produce multiple images of a single quasar?
• RQ2 What is the role of time-delays between lensed images in estimating the Hubble parameter H₀?
• RQ3 How do microlensing effects from stars in the lensing galaxy influence the observed image configurations and magnifications?
• RQ4 What recent observational and theoretical advances have improved the accuracy of H₀ measurements using quasar lensing?

Key findings

• Multiple images of a single quasar are produced due to strong gravitational lensing by intervening massive galaxies.
• Time-delays between the arrival of light from different lensed images provide a direct method to estimate the Hubble parameter H₀.
• Microlensing by stars in the main lensing galaxy contributes to observed image magnification and de-magnification patterns.
• Recent progress in modeling lensing systems has improved the precision of H₀ estimates using quasar lensing.