Weak gravitational lensing with CO galaxies

TL;DR

This paper explores the potential of using CO-emitting galaxies observed with ngVLA for weak gravitational lensing, offering a complementary approach to optical surveys to improve systematic error control and enhance cosmological insights.

Contribution

It proposes a novel radio/microwave weak lensing method using CO galaxies, providing a complementary systematic approach and additional data types for future cosmological surveys.

Findings

Radio CO galaxy lensing has different systematics from optical surveys.

Combining optical and radio lensing can validate and improve cosmological measurements.

ngVLA observations can offer spectral and polarimetric data for new analyses.

Abstract

Optical weak lensing surveys have become a powerful tool for precision cosmology, but remain subject to systematic effects that can severely bias cosmological parameter estimates if not carefully removed. We discuss the possibility of performing complementary weak lensing surveys at radio/microwave frequencies, using detections of CO-emitting galaxies with resolved continuum images from ngVLA. This method has completely different systematic uncertainties to optical weak lensing shear measurements (e.g. in terms of blending, PSF, and redshift uncertainties), and can provide additional information to help disentangle intrinsic alignments from the cosmological shear signal. A combined analysis of optical and CO galaxy lensing surveys would therefore provide an extremely stringent validation of highly-sensitive future surveys with Euclid, LSST, and WFIRST, definitively rejecting biases due to residual systematic effects. A lensing survey on ngVLA would also provide valuable spectral (kinematic) and polarimetric information, which can be used to develop novel cosmological analyses that are not currently possible in the optical.