We can map the evolution of galaxies directly through observations of the distant universe, which provide us with snapshots of the galaxy population at earlier epochs. Practical challenges involve measuring the physical properties of the very faint targets, such as their stellar mass and star formation rate. The most interesting scientific and conceptual issues are how to relate the observed snapshots to the actual evolutionary fates of the galaxies.
- How does the star formation rate depend on stellar mass?
- Are there ultra-compact, massive galaxies in the early universe?
- How did galaxy disk sizes evolve?
The properties of the nearby (and hence present-day) galaxies are remarkably regular. We're studying the detailed structure of galaxies to understand why.