IRMaGiC: Extending Luminous Red Galaxy Selection into the Infrared with Joint Rubin Observatory’s Large Survey of Space Time and Roman’s High Latitude Imaging Survey

We introduce IRMaGiC, an algorithm built on RedMaGiC designed to enhance the selection of Luminous Red Galaxies (LRGs) across the redshift range \(1 \leq z \leq 2\). We show that this method extends the capabilities of the RedMaGiC algorithm by applying it to simulated photometric data from the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) and the Nancy Grace Roman Space Telescope’s High Latitude Imaging Survey (HLIS). By integrating infrared band coverage from Roman HLWAS with LSST’s optical bands, IRMaGiC enables red-sequence calibration at higher redshifts. We demonstrate that IRMaGiC reduces scatter and bias in photometric redshift estimates for LRGs at higher redshift, providing more accurate redshift assessments compared to existing methods. Our findings suggest that incorporating infrared data can considerably improve the selection and redshift estimation of LRGs at higher redshift, offering substantial benefits for future cosmological surveys.