Globular clusters are a tight aggregation of hundreds of thousands to millions of stars. They are very old, devoid of gas, and have stellar populations that share the same age and chemical composition. To give you an idea of how old these systems are, it’s known that the Milky Way's globular clusters have ages ranging from 10-15 billion years. This means that these clusters could be relics of the formation of the Milky Way itself!
Empirical observations show that globular cluster luminosities are roughly proportional to the stellar mass of their host galaxy, which suggests that the formation of globular clusters and galaxies are related. However, how they are related is currently not well understood.
Although globular clusters are interesting in their own right, and can fill many books, I'm particularly interested in what they can tell us about galaxy evolution. There are two competing theories about cluster formation, with different implications about galactic evolution depending on which model is correct:
My suspicion is that clusters form in both these ways. The question, then, is which of these processes dominate cluster formation?
If Model 1 is correct, then the large star formation processes that produced globular clusters must have ceased a long time ago. Could this give us information about how galaxies evolved in the young universe? What would give rise to such vigorous star formation in the past, but not today?
If Model 2 is correct, could we then infer the metallities and kinematics of progenitor galaxies? What kinds of progenitor galaxies merged to form the large galaxies we see today? Is it possible large galaxies formed from a couple of gas-rich mergers? In that case, we'd expect to see over densities in globular cluster populations. Or, do large galaxies form from many mergers? If this is the case, the gases in the progenitor galaxies may have been used up in star formation from the multiple merging events, which could effectively deplete the materials needed for cluster formation. Perhaps this could provide another avenue to study the poorly understood physics of galactic mergers in general, such as gas heating and cooling, feedback from star formation, and the complex interplay between them.
I do not have the spectroscopy needed to date globular clusters, or to distinguish between different populations. However, I do have survey data of a large number of galaxies (on the order of thousands) from the Spitzer Space Telescope. I plan on looking at globular cluster populations to see if there are any over densities, and if so, what those over densities are related to. I do have some candidates that look promising, but at this point, it's too early to tell. Automating the detection and data reduction process has been difficult these past few months, but the prize is well worth the effort: a glimpse into galactic history.
Note: All of these images (except the top one of M80, which I jacked off of Wikipedia) come from the work of West, Cote, Marzke, and Jordan. They wrote a wonderful review paper in Nature on this very topic. If you're interested, I suggest you click here: