The stellar populations of extragalactic globular clusters

Globular clusters are dense collections of hundreds of thousands of stars found around all bright galaxies. Being much brighter than individual stars, globular clusters can be studied at much greater distances. In my thesis I studied the chemical compositions of over a thousand globular clusters around thirteen galaxies. By measuring the ratio of hydrogen to heavy elements such calcium in the globular clusters and using these ratios to infer relative ages, I was able to study the formation history of these globular clusters. By understanding more about how globular clusters form, I was able to learn about how galaxies form.