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Nichol and Matt go to Chile!

Archive for globular clusters

Clusters, Courses and Everything in Between

As foreshadowed in our most recent post, I thought I’d provide an update on some of my recent astronomy related goings-on. Since March, I’ve been pretty busy with the first few courses of my program as well as trying to fit in some time to work on a bit of data in regard to what will eventually be my thesis. My course work thus far has involved assignments, preparing/giving three 45-minute seminar talks and now the focus is mostly on completing two significant research projects. Two of my talks have been on summarizing recent major review papers. The first was on the idea of a universal stellar initial mass function (don’t ask…you don’t want to know), and the second was a review of what the community knows about the formation of massive young star clusters, the sort that I will be studying in detail for the next few years. The other talk was a lecture to my stellar variability class on various techniques of determining pulsational periods of variable stars…thrilling I know.

As far as the thesis goes, thus far there is exactly zero interesting information to report. Indeed, when time has permitted, I’ve just been trying to reduce some data taken of some large star clusters in the galaxy NGC 5128, or Centaurus A as it’s also called. Unfortunately, the most important task in astronomical observations, transforming what we get from telescopes into clean, usable data, is also one of the hardest, most frustrating and challenging parts. I’m hoping that after the semester is finished at the end of June, that I can work full-time on getting these spectra reduced so that I can move on to the fun part: analysis. In this case, I’ll be trying to measure what kind of chemical abundances are in the clusters, e.g. how much carbon, magnesium, calcium, iron, etc., the systems have. These measurements will tell me what kind of star formation has happened in the past, since all of those elements are created on different timescales by different types of stars. In the long-term, I’ll hopefully be creating some computer models that simulate how such massive groups of stars evolve, and most importantly, form. The observed measurements, combined with those of clusters in other galaxies (and galaxy clusters) will serve as a good test to see if my models may actually be accurate representations of how these structures form.

I’m also working on two other research projects as part of this semester’s courses. For my extra-galactic course, I’m working with two other students on collecting information on a large sample of galaxy clusters in order to compare to work that has previously been done. We’re still quite early in the project though, so I don’t have too much to say about it other than that. This project will be very challenging in that it involves a subject of astronomy that I’m not very familiar with, so it will be interesting to see how it develops.

My other project is being done as part of my stellar variability course. I’m working with another PhD student on this, and so far it is coming along very well! With fingers crossed, we’re hoping to complete a report that might be submitted for publication since the subject matter is quite contemporary. The object we are studying, NGC 6569, is similar to the objects that I’m studying in Centaurus A; it is a collection of a few hundred thousand stars called a globular cluster (GC), in the bulge of the Milky Way. Specifically what we are doing is searching for variable stars, i.e. stars that periodically get brighter and dimmer, and plotting how the stars’ brightnesses change over time. This GC is interesting in that the ‘metallicity’, or how much of the cluster’s stars are made of elements heavier than H or He, is quite high compared to other GCs. Some recent work has suggested that variable stars in other high-metallicity GCs seem to have longer periods, i.e. they take a longer time for their brightnesses to increase and fade, than the same types of variable stars found outside of clusters. It will be interesting to see what kind of results we get. Will they have longer periods, or will they be more in line with what is expected from other GCs? Will the results point toward a fundamentally different sub-class of this type of variable star? One way or another, hopefully we’ll end up with a report that will be interesting to the theorists who incorporate these observational constraints into their models. As well, since these types of variable stars are used as ‘standard candles’, which can be used to estimate distances, this kind of work may effect current distances estimates that have already been done. We’ve still got a lot of work to do, but things are looking promising so far. To bring this update to a close, I’ll just leave this here…

The globular cluster NGC 6569. I wish I could take credit for the gorgeous image, but this was made from our data by my partner. The one I made was nice, but not this nice!

-M