Target Selection for the DESI Peculiar Velocity Survey

We describe the target selection and characteristics of the DESI Peculiar Velocity Survey, the largest survey of peculiar velocities (PVs) using both the fundamental plane (FP) of galaxies and the Tully-Fisher (TF) relationship planned to date. We detail how we identify suitable early-type galaxies for the FP and suitable late-type galaxies for the TF relation using the photometric data provided by the DESI Legacy Imaging Survey DR9. Subsequently, we provide targets for 373 533 early-type galaxies and 118 637 late-type galaxies within the DESI 5-year footprint. We validate these photometric selections using existing morphological classifications. Furthermore, we demonstrate using survey validation data that DESI is able to measure the spectroscopic properties to sufficient precision to obtain PVs for our targets. Based on realistic DESI fiber assignment simulations and spectroscopic success rates, we predict the final DESI Peculiar Velocity Survey will obtain $\sim$133 000 FP-based and $\sim$53 000 TF-based PV measurements over an area of 14 000 $\mathrm{deg^{2}}$. Each of these components will be a factor of 4--5 larger than other recent samples. We forecast the ability of using these data to measure the clustering of galaxy positions and peculiar velocities from the combined DESI PV and Bright Galaxy Surveys (BGS), which allows for cancellation of cosmic variance at low redshifts. With these forecasts, we anticipate a $4\%$ statistical measurement on the growth rate of structure at $z<0.15$. This is over two times better than achievable with redshifts from the BGS alone. The combined DESI PV and Bright Galaxy surveys will enable the most precise tests to date of the time and scale dependence of large-scale structure growth at $z<0.15$.