Collaborative Research: NSF BSF: Disk Formation over Cosmic Time

Most of the stars that make up our home galaxy, the Milky Way, are arranged in the shape of a rotating disk. Many other galaxies in the universe today are also shaped like disks. However, when astronomers look back in time with large telescopes, they see that the fraction of galaxies that are disks goes down.

The very first galaxies we have seen in the primordial universe are not disks. The investigators will use simulations that model the formation of galaxies, from the earliest times to today. They will explore when and how galaxies begin to take the shape of disks to understand the reasons why.

The investigators will also compare their simulations to observations of stars in the Milky Way and distant galaxies to help us understand how disk galaxies came to be. The research program will support the education and training of PhD students, increasing their understanding of physics, data science, scientific visualization, and programming. The investigators will also mentor a diverse population of undergraduate students pursuing careers in STEM fields.

The investigators will study the physics that underpins galaxy disk formation using a large set of zoom cosmological simulations with Feedback In Realistic Environments (FIRE) galaxy formation physics. They will study the connection and causal correlations between thin and thick disks: Do thin disks emerge first in cosmic history, with thick disks constituting a descendant, heated population?

Or, are thin disks a relatively recent phenomenon, with thick disks a natural outcome of high-redshift galaxy formation? The investigators will explore the degree to which galaxy potentials becoming centrally concentrated over time may help enable galaxies to “spin up,” and track how the disordered interstellar medium (ISM) of galaxies at early times transitions to more ordered, thin-disk-dominated populations at late times.

A crucial component of this work will be to understand the astrophysics that regulates galactic disk formation as a means of understanding what may be missing in models that do not produce disks with the correct frequency and character to match observations. The simulations will allow the investigators to explore connections between the baryon cycle and morphological structure.

The investigators will inform deep-field imaging and velocity-field studies of galaxy disk “settling” as well as local studies with surveys including MaNGA, the Local Volume Mapper, GALAH, and Gaia.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.