Kinematic lensing with the Roman Space Telescope

Kinematic lensing (KL) is a new cosmological measurement technique that combines traditional weak lensing (WL) shape measurements of disc galaxies with their kinematic information. Using the Tully–Fisher relation, KL breaks the degeneracy between intrinsic and observed ellipticity and significantly reduces the impact of multiple systematics that are present in traditional WL. We explore the performance of KL given the instrument capabilities of the Roman Space Telescope, assuming overlap of the High Latitude Imaging Survey (HLIS) and the High Latitude Spectroscopy Survey (HLSS) over 2000 deg². Our KL suitable galaxy sample has a number density of n_gal = 4 arcmin⁻¹ with an estimated shape noise level of σ_∊ = 0.035. We quantify the cosmological constraining power on Ω_m–S₈ and w_p–w_a by running simulated likelihood analyses that account for redshift and shear calibration uncertainties, intrinsic alignment, and baryonic feedback. Compared to a traditional WL survey, we find that KL significantly improves the constraining power on Ω_m–S₈ (FoM_KL = 1.70FoM_WL) and w_p–w_a (FoM_KL = 3.65FoM_WL). We also explore a ‘narrow tomography KL survey’ using 30 instead of the default 10 tomographic bins; however, we find no meaningful enhancement to the figure of merit even when assuming a significant time dependence in our fiducial dark energy input scenarios.