Fractured but Whole: Towards Understanding the Smallest Substructure of the Milky Way
University of Notre Dame
The Milky Way is believed to have formed through hierarchical mergers to form the structure observed today. Galaxies incorporated into the Milky Way have their stars scattered and displaced, no longer retaining the spatial coherence they once had. To understand these mergers and their impact on the structure of the Milky Way is a fundamental goal of Galactic Archaeology, one which is possible thanks to recent advancements in both observational and computational astronomy. In this work, data sets are assembled from large-scale surveys to discover the smallest of these mergers, put them in context with the currently known Milky Way structure, and track chemical evolution progress throughout the Galaxy. Associations of remnants to known Milky Way substructures are recovered, such as Gaia-Sausage-Enceladus, Helmi Streams, Thamnos, Splashed Disk, Metal-Weak Thick Disk, and LMS-1 (Wukong). Previously discovered remnants are for the first time analyzed in exhaustive detail to compare relations between discoveries, showing remarkable consistency across the field even when using differing detection methods. Evidence of remnants connected to Globular Clusters is presented, while no known Dwarf Galaxy connections are recovered. Chemically peculiar stars are collected and analyzed in the largest sample to date, with the birth environments of these remnants analyzed at the elemental level (C, Mg, Sr, Y, Ba, and Eu). This work presents a crucial step towards understanding the smallest substructure of the Milky Way.
Hosted by Prof. Beers