The 3D motion of the Interstellar Medium with ESO and ESA telescopes

The current model for the structure of the local Milky Way is in crisis.

Data from the ESA Gaia mission has overthrown the 150-year-old paradigm for the gas distribution in the local Milky Way, a 500 pc ring known as Gould’s Belt. In the newly emerging view, local star-forming regions are connected by lower-density gas. They are part of a new organizational unit: undulating, coherent, and linear Galactic-scale gas structures.

What is the origin of these kpc-long structures, how do star-forming regions form and disperse inside them, and are they related to the traditional view of spiral arms?Underpinning these questions lies a critical measurement currently beyond reach: tracing the gas flow in 3D. Gas flow is a fundamental physical property of the ISM.

Knowing it is to know the past and future path of the gas in the Galaxy, measure momentum, and infer the external forces acting on the star-forming gas.

Achieving this measurement for the local kpc would constitute a breakthrough in ISM, star formation, and spiral structure formation research. The goal of ISM-FLOW is to see the local Milky Way gas in 3D motion for the first time and make sense of it.

The project will use a dedicated (and approved) large observational campaign in the near-infrared at ESO (VISIONS, PI: Alves) and upcoming ESA Gaia data.

I have been developing new methods over the past decades to determine cloud distances, shapes, and motions using space and ground-based data and have proven feasibility.

We will measure the local gas flow for the first time, derive the local molecular gas trajectory from the past and into the future (-20 to 20 Myr), and be in a position to make significant advances in the field and leave a legacy to the community.

We will 1) characterize the newly discovered large-scale structures, 2) understand the formation and dispersal of giant molecular clouds and star formation regions, and 3) confront gas flow theories and the formation of spiral arms.