The History of Star Formation in Galaxies

TL;DR

Understanding galaxy formation requires detailed star formation histories, which can be achieved through advanced multi-band photometry and future observational capabilities to study diverse and crowded galaxy regions.

Contribution

The paper emphasizes the need for improved observational tools to extend resolved stellar population studies to larger, more diverse galaxy samples and crowded regions.

Findings

Hierarchical galaxy assembly supported by observations

Resolved stellar populations reveal star formation and chemical evolution histories

Future capabilities will enable comprehensive studies of galaxy evolution

Abstract

If we are to develop a comprehensive and predictive theory of galaxy formation and evolution, it is essential that we obtain an accurate assessment of how and when galaxies assemble their stellar populations, and how this assembly varies with environment. There is strong observational support for the hierarchical assembly of galaxies, but our insight into this assembly comes from sifting through the resolved field populations of the surviving galaxies we see today, in order to reconstruct their star formation histories, chemical evolution, and kinematics. To obtain the detailed distribution of stellar ages and metallicities over the entire life of a galaxy, one needs multi-band photometry reaching solar-luminosity main sequence stars. The Hubble Space Telescope can obtain such data in the low-density regions of Local Group galaxies. To perform these essential studies for a fair sample of the Local Universe, we will require observational capabilities that allow us to extend the study of resolved stellar populations to much larger galaxy samples that span the full range of galaxy morphologies, while also enabling the study of the more crowded regions of relatively nearby galaxies. With such capabilities in hand, we will reveal the detailed history of star formation and chemical evolution in the universe.