Science

Designing a data collection to constrain how stars form in the Milky Way 

MilkyWay3D.org is consolidating a wide variety of datasets relevant to understanding the physical processes that shape cloud and star formation in our Milky Way. 
The assembled datasets offer 3D:

• maps of density, velocity, mass, and sometimes temperature of interstellar material

• characterizations of clouds, shells and voids

• positions and motions of OB associations, stellar clusters, HII regions, and supernova remnants

• derived structures, such as spiral arms, proposed as significant by researchers.

Using spatial and kinematic information together,
MilkyWay3D.org holdings can constrain

• the evolutionary state of the gas and stellar associations (e.g. forming, dissolving)

• spatial, dynamical, and temporal connections between gas, young stars

• sources of feedback across a range of scales and over a diverse set of galactic environments. 

What kind of specific questions can be asked, addressed, and perhaps answered? 

• What fraction of star-forming clouds are or are not candidates for having been compressed at bubble surfaces, and/or at bubble intersections?

• What fraction of star-forming gas features cannot be clearly associated with structures at least an order-of-magntidue larger than they are? (How much "free-floating" dense gas is there in the local ISM?)

• What sources of feeback (stellar winds, supernovae, etc.) are most relevant on what spatial and temoral scales?

• Can we use information about cluster populations and ages to constrain the bulk motions and expansions of feedback-driven cavities?

• How do "young stars leave home"? What fraction of stars drift away, at what speed, or do clouds "dissolve" first? How often might young stars drift from one star-forming cloud to another?

• Are the topological characterizations of the spatial distribution of interstellar gas  (in)/consistent with any particular numerical simulation(s)?

• How well can data, simulations, or both constrain the history of star formaiton in a given region? Over what time scale?  For example, over what spatial or temporal scale is it possible to typically associate a star cluster with a gas cavity? 

• Are there clear relationships between the properties of gas and stars and their position or motion with respect to significant Galactic structures, such as the mid-plane or large-scale features, including spiral arms?

• What are the dominant mechanisms shaping molecular cloud formation and destruction? 

• How are these mechanisms related to clouds’ physical properties and the larger-scale galactic environments?

• What is the relationship between interstellar cavities and the distribution of OB associations, supernova remnants, and HII regions?

• Do we observe evidence for triggered star formation at the surfaces of these cavities? 

• What role does Galactic structure play in star formation? Are spiral arm-like structures in the Milky Way quasi-stationary or transient features? Do these arm-like structures violently induce shocks or gently accumulate gas? If the former, what role do spiral shocks play in star formation?

Beyond the Milky Way?

Ultimately, MilkyWay3D.org will not only lay the framework for addressing these questions, but the new "face-on" view of our own Galaxy it will offer will alo provide a strong basis for comparison with resolved studies of cloud and star formation in nearby-face on spiral galaxies with JWST.  By contextualizing results in light of the nearby galaxy population, MilkyWay3D.org will provide crucial new constraints on how “unique” our Milky Way is at this moment in time, a key piece of information underpinning all galactic to extragalactic star formation comparisons.