Combining Spectroscopic And Imaging Galaxy Surveys For Improved Measurements Of Large-Scale Structure

Large galaxy imaging surveys promise to deliver extraordinary datasets to answer open questions about the nature of dark matter and dark energy, but these surveys suffer from challenges arising from the difficulty in constraining galaxy redshift. My thesis work leverages spectroscopic observations of small, well selected subsets of galaxies observed in imaging surveys to improve the utility of photometric datasets for cosmological studies. First, I will describe the new methodology designed to optimize use of overlapping spectroscopic information for the Dark Energy Survey Year 3 galaxy lensing analysis and exhibit the resulting cosmology constraints. Second, I will present a novel algorithm for accurately propagating uncertainties of probability distributions and illustrate the value of this algorithm for redshift calibration. Finally, I will show results using spectroscopy of galaxy cluster members to measure the impact of projection effects on clusters and comment on how this relates to optical cluster cosmology results. This thesis presents promising paths forward to take full advantage of forthcoming surveys to constrain the cosmological model.