The Bird’s Eye Milky Way: Gaia’s view on the density diagnostics of star formation

Understanding star formation is a key element in our efforts to understand the Universe we live in.

One main obstacle hindering progress is that for decades, the field of star formation has been bifurcated into two communities that view the same process from vastly different vantage points: the galactic and extragalactic perspectives.

While these perspectives are highly complementary, observational limitations have dictated that interfacing them is simply not possible.

This has severely affected our ability to develop a holistic picture of star formation.However, the coming decade will change this: we will be able to concretely tie together the local physical processes studied in the Milky Way and the global ones studied in nearby galaxies.

The spatial scales studied in our galaxy and in others have begun to overlap and interfacing the two communities has become one focus point of star formation studies. With this project, we will target this interface from a unique and novel angle.

Recently, the Gaia space observatory has revolutionized the mapping of Milky Way dust distributions—for the first time, we can reveal the true 3-dimensional (3D) distribution of the dust, as opposed to plane-of-the-sky projections.

Such information is already rewriting our picture of local interstellar medium and impacting the star formation and molecular cloud evolution models.

We will make use of the 3D, Gaia-derived dust distributions to make a progress in understanding the density structure of the local interstellar medium and the connection of that structure to star formation.

In our current knowledge, the density structure of gas across a wide range of densities is linked to the evolution of molecular clouds, and therefore, to star formation.

Gaia data can trace this distribution relatively sensitively, allowing access to a density regime that is not easily accessible in the Milky Way, but standardly observed in external galaxies.

By doing this, we provide unique information on the density structure of gas in the Milky Way and a concrete way to better interface Galactic and extragalactic ISM/star formation knowledge.

Specifically, this project will quantify the gas density statistics, namely the probability density functions of gas density (PDFs) and their scale dependency, in a complete volume within the Milky Way disk; this has not been done using 3D data before. We will also improve our picture of the exact 3D dust distribution in the Solar neighbourhood.

Finally, we will shed new light on the kinematics of molecular gas by exploring a combination of 3D dust and CO gas data.Together, the goals above enable us to view the gas distribution of the Milky Way from a “Bird’s Eye perspective”, throughout different scales.

The resulting—currently missing—information is transformational for decoding the physics hidden in the observational star formation relations and diagnostics.The project will be conducted in four years by a PhD student.

The student will be advised by the PI and a collaborating Gaia dust mapping expert. 4.4 full-time-equivalents (FTEs) are requested; 4 FTEs for the student and 0.4 for the PI for supervision and project management.