Crowded Field Photometry with Rubin: Exploring 47 Tucanae with Data Preview 1

We analyze imaging from Data Preview 1 of the Vera C. Rubin Observatory to explore the performance of early LSST pipelines in the 47 Tucanae field. The coadd-object catalog demonstrates the depth and precision possible with Rubin, recovering well-defined color–magnitude diagrams for 47 Tuc Small Magellanic Cloud. Unfortunately, the existing pipelines fail to recover sources within ∼28 pc of the cluster center, due to the extreme source density. Using Rubin’s forced photometry on stars identified via Difference Imaging, we can recover sources down to ∼14 pc from the cluster center, and find 14,744 potential cluster members with this extended data set. While this forced photometry has significant systematics, our analysis showcases the potential for detailed structural studies of crowded fields with the Rubin Observatory.