Kinematic Lensing with the Dark Energy Spectroscopic Instrument -- Probing structure formation at very low redshift

TL;DR

This paper proposes a Kinematic Lensing survey using DESI to probe low-redshift structure formation, offering potential insights into the $S_8$ tension and complementing other cosmological surveys.

Contribution

It introduces a novel Kinematic Lensing method with DESI, demonstrating its potential to constrain low-redshift structure formation and address cosmological tensions.

Findings

DESI-KL can constrain $\sigma_8(z<0.15)$ effectively.

Combining DESI-KL with LSST enhances cosmological insights.

The method offers additional science cases like modified gravity and dark matter studies.

Abstract

We explore the science prospects of a 14,000 deg$^2$ Kinematic Lensing (KL) survey with the Dark Energy Spectroscopic Instrument (DESI) and overlapping imaging surveys. KL infers the cosmic shear signal by jointly forward modeling the observed photometric image and velocity field of a disk galaxy. The latter can be constrained by placing multiple DESI fibers along the galaxy's major and minor axis, a concept similar to the DESI Peculiar Velocity Survey. We study multiple subset galaxy samples of the DESI Legacy Survey Data Release 9 catalog and quantify the residual shape noise, $\sigma_\epsilon$, of each sample as a function of cuts in $r$-band magnitude using mock observations. We conduct simulated likelihood analyses for these galaxy samples and find that a DESI-KL program can place highly interesting constraints on structure formation at very low redshifts, i.e. $\sigma_8(z<0.15)$. We conclude that if the $S_8$ tension consolidates as a phenomenon, a DESI-KL survey can provide unique insights into this phenomenon in the very late-time Universe. Given the different footprints of DESI and Rubin Observatory's Legacy Survey of Space and Time (LSST), lensing results from both surveys are highly complementary and can be combined into a joint lensing survey. We further note that DESI-KL benefits multiple additional science cases, e.g. studies of modified gravity models when combined with peculiar velocity surveys, and dark matter studies that are based on galaxy-galaxy lensing of dwarf galaxies.