Mining Ultra-Faint Galaxies in the Local Group: Are Missing Satellites All Found?
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Abstract: Ultra-faint dwarf (UFD) satellite galaxies are believed to have the oldest, most dark-matter-dominated, and least chemically evolved stellar populations. Therefore, UFDs serve as effective cosmological probes for the early stage of the Universe. In this study, we applied unsupervised machine learning (DBSCAN & OPTICS) to search for potential UFDs by analyzing spatial overdensities of the tip of red giant branch (TRGB) stars in the DELVE survey. Our objective is to complement the current catalog of UFDs in the local volume while exploring the potential of using modern statistical density searching tools in UFD studies. We have focused on searching for M31 UFDs and recovered all 10 M31 satellite galaxies in the DELVE DR2 coverage. This work provides tools to identify UFDs in large sky surveys, which helps to test the cosmological constraints of the Lambda Cold Dark Matter (ΛCDM ) model.