Kinematic Lensing Ratio: Reviving Weak Lensing Cosmography as a Geometric Dark Energy Probe

TL;DR

The paper introduces the kinematic lensing ratio (KiLeR), a new geometric method using weak lensing and galaxy kinematics to improve dark energy constraints and mitigate systematics.

Contribution

It presents KiLeR as a novel approach that reduces key systematics in weak lensing cosmography and forecasts significant improvements in dark energy measurements.

Findings

Forecasts a 192% improvement in dark energy constraints with KiLeR for Roman.

Demonstrates KiLeR mitigates systematics like redshift errors and intrinsic alignments.

Discusses observational pathways and requirements for implementing KiLeR.

Abstract

We introduce the kinematic lensing ratio (KiLeR), a geometric dark-energy probe from weak lensing. Combining shear ratios with intrinsic galaxy shapes inferred from kinematics, KiLeR naturally mitigates most first-order lensing systematics, including redshift errors, intrinsic alignments, and baryonic effects. The forecast on Roman shows a 192% improvement in the state-of-the-art dark energy constraints from adding KiLeR, providing independent tests of the evolving dark energy hint in the DESI DR2 BAO+CMB+SN analysis. We quantify the science requirements on systematic and statistical error control and discuss the pathways towards KiLeR observation.