CMB Cluster Lensing: Cosmography with the Longest Lever Arm

TL;DR

This paper explores using gravitational lensing of the CMB and galaxies by clusters to improve measurements of dark energy, leveraging the CMB's well-known distance and longer lever arm for enhanced sensitivity.

Contribution

It introduces a method combining galaxy and CMB lensing to measure cosmographic distances, highlighting advantages of using the CMB as a source plane for dark energy studies.

Findings

Potential to reach statistical sensitivity with upcoming surveys

Can provide consistency tests of the cosmological constant model

Future measurements could achieve 1% precision in convergence

Abstract

We discuss combining gravitational lensing of galaxies and the cosmic microwave background (CMB) by clusters to measure cosmographic distance ratios, and hence dark energy parameters. Advantages to using the CMB as the second source plane, instead of galaxies, include: a well-determined source distance, a longer lever arm for distance ratios, typically up to an order of magnitude higher sensitivity to dark energy parameters, and a decreased sensitivity to photometric redshift accuracy of the lens and galaxy sources. Disadvantages include: higher statistical errors, potential systematic errors, and the need for disparate surveys that overlap on the sky. Ongoing and planned surveys, such as the South Pol Telescope in conjunction with the Dark Energy Survey, can potentially reach the statistical sensitivity to make interesting consistency tests of the standard cosmological constant model. Future measurements that reach 1% or better precision in the convergences can provide sharp tests for future supernovae distance measurements.