Speaker
Description
Within the Local Arm Structure project we investigate the three-dimensional distribution and vertical kinematics of young tracers in the Orion (Local) arm using Gaia astrometry and recent catalogues of open clusters and star-forming regions. Building on our results in Vertical kinematics of the young Galactic clusters (Alfaro, Sánchez-Gil & Elmegreen 2025, MNRAS, doi:10.1093/mnras/staf155), we show that clusters younger than ≲30 Myr define an almost linear relation in the V_Z plane, consistent with a vertical harmonic oscillator and providing independent constraints on the effective local mass density.
In this flash talk I will present our ongoing work on the spatial structure of the Local Arm and its surroundings, aiming to characterise the nature of arm segments and filamentary groupings, including candidates for inter-arm structures. Using the 3D positions (X,Y,Z) of young clusters and associations, we apply minimum spanning tree (MST) analysis and Gaussian Mixture Model (GMM) classification to identify coherent structures and quantify their geometry, connectivity, and contrast with respect to the underlying disc. I will also outline how adding near-infrared astrometry from a GaiaNIR-like mission would allow us to extend this analysis into highly extincted regions, tracing these filaments and arm segments where Gaia alone becomes incomplete and testing whether their properties change between optically visible and dust-obscured parts of the spiral pattern.
