Tracing the Milky Way’s Past with HDBSCAN: Finding the Ghosts of Ancient Galaxies
Andrea Sante and collaborators test the HDBSCAN clustering algorithm to trace the Milky Way’s merger history using Auriga simulations. By optimizing parameters and using a 12-dimensional feature space, they show HDBSCAN reliably identifies recent stellar streams but struggles with older, well-mixed debris. Contamination from stars formed inside the Milky Way further limits recovery, though cluster purity remains high.
How the Milky Way’s Disc Survived a Cosmic Collision
This paper explores how the Milky Way’s disc formed and survived an ancient collision with the Gaia-Sausage-Enceladus galaxy. Using simulations and Gaia data, Orkney and colleagues show the disc was already spinning about 11 billion years ago and that the merger was likely minor, not major. Despite disruption, the disc reformed, with starbursts and globular clusters marking the event’s impact.
How Galactic Collisions Sculpt the Cosmos: The Impact of Merger Orbits on Galaxy Structure
Wu et al. study how the paths of galaxy mergers affect the resulting structure using simulations. They find that spiral-in orbits tend to preserve disks, while head-on collisions destroy them and build bulges and halos. The hot inner stellar halo grows in nearly all mergers, making it a strong indicator of merger history.