Large-Scale Structure Cosmology with Rubin’s Large Survey of Space and Time and Roman Space Telescope in the Near-Infrared

Abstract

Understanding how structure forms and evolves in the Universe is a central goal of modern cosmology. By mapping the large-scale distribution of galaxies, we can probe the physical nature of dark matter and dark energy, which together govern the growth of cosmic structure. Upcoming wide-field imaging surveys, including the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) and the Nancy Grace Roman Space Telescope, will observe the sky with unprecedented depth and coverage, enabling precise measurements of galaxy clustering over vast cosmic volumes. Among the most important tracers of large-scale structure are luminous red galaxies (LRGs), which are intrinsically bright and can be detected at great distances. Extending observations from optical to near-infrared wavelengths with these two surveys significantly enhances our ability to identify and characterize these galaxies across a wider range of cosmic history. Access to longer wavelengths provides additional information about galaxy properties and improves the reliability of distance estimates derived from observations. Realizing the full scientific potential of these surveys, however, requires careful control of observational uncertainties and robust methods for estimating galaxy distances. Combining optical and near-infrared measurements is therefore essential for achieving accurate and stable constraints on the growth of cosmic structure in the coming generation of cosmological surveys.My PhD research focused on addressing key challenges in near-infrared cosmology and strengthening the synergy between LSST and Roman for identifying luminous red galaxies. For LSST, I characterized and simulated sensor-related systematics in near-infrared–adjacent imaging, developing a framework to model instrumental effects that could bias measurements. For Roman, I developed realistic near-infrared spectroscopic imaging simulations to evaluate galaxy selection and distance estimation performance under survey-like conditions. By combining the complementary strengths of LSST’s wide-area optical imaging and Roman’s near-infrared spectroscopic capabilities, I developed methods to improve the identification and calibration of luminous red galaxies across survey footprints. This joint analysis framework enhances the robustness of galaxy selection and distance estimation, helping unlock the full cosmological potential of next-generation surveys.