The Dynamics of the Milky Way: Unveiling the 6D Skeleton of Star Formation in the 2040s

TL;DR

By targeting the $6D$ phase-space distribution of young MW populations, the paper outlines a plan to connect Galactic-scale dynamics with local star formation. It argues for a new, large-scale spectroscopic facility that complements GaiaNIR, Rubin LSST, and the Roman Telescope to map distances, motions, and stellar ages across the disk, including obscured regions. The core questions probe whether large-scale instabilities or local feedback primarily drive star formation, and whether stars form exclusively in clusters or also in diffuse strings, with implications for the star formation history and the cluster formation efficiency. The proposed framework aims to deliver a dynamic, $6D$ model of the MW that serves as a benchmark for interpreting extragalactic star formation and for understanding the Milky Way's evolutionary trajectory.

Abstract

The Milky Way (MW) is our unique laboratory to test star formation theories at the level of individual stars, serving as the Rosetta Stone to interpret extragalactic observations. The proposed White Paper focuses on the following key questions regarding the structure and evolution of the MW traced by young stellar populations: Q1. How do large-scale dynamical instabilities, like warps and vertical waves, drive the star formation of the Galactic thin disk? Q2. Do star-forming regions form stochastically, driven by local self-propagating feedback, or are they triggered by a common dynamical process acting on Galactic scales? Do internal feedback loops and external interactions tend to sustain or quench star formation in the MW? Q3. Are the clustered star-forming regions the only environments where stars form, or can stars also form in more diffuse structures such as the stellar strings?

Figures (1)

• Figure 1: Fig.1 Map of the predicted number of stars younger than 10 Myr down to 0.3 $M_\odot$ per HEALPix ($N_{side} = 64$) shown in equatorial Mollweide projection. The counts are computed following the metric used in pris23, incorporating the 3D dust map and crowding effects based on the Rubin LSST Opsim. The map represents the sources detectable down to the limiting magnitudes corresponding to an accuracy level of $\sigma = 5$ in the $g, r, i$ bands over the full 10-year survey. Adapted from Prisinzano et al. pris23.