Written by Michael Rutkowski, Junior Researcher ’11-12

Without exception, my introduction in Korea goes as follows:

Them: “So, what are you doing here in Korea?”
Me: “Oh, I’m studying astrophysics at Yonsei University.”
Them: “Whoa! But why are you in Korea?”

The answer to this question is straightforward: I collaborate with a research team at Yonsei University that focuses on the same topics I address in my Ph.D. research.  For most, this isn’t a satisfactory response, so I usually whet their appetite with some facts about South Korea’s unique history in astronomy and astrophysics.

Did you know that in 1395, at a time when “the West” was struggling to free itself from its self-imposed “Dark Ages,’’ the Joseon Dynasty was completing the world’s first star map, which incorporated stellar maps first recorded as early as the first century during the Goguryeo Dynasty? Did you know that the first Korean to receive a Ph.D. in science was Lee Won Chol for his work in astronomy, and that he was a graduate of Yonhee (Yonsei, pre-Severance) University?

At this point, if my conversation partners are still around, I realize what they want to hear about is my research at Yonsei.  So, I suggest they grab a chair, because if we’re going to discuss my research properly, we really need to start from the beginning.

About 13.7 billion years ago, everything that was, is, or will be — i.e., “the universe” — was born in an event casually referred to as “the Big Bang.” (This event occurred approximately 13.7 billion years before the second “Big Bang” of which many more Koreans are aware.) A couple billion years or so after the birth of the universe, conditions were finally adequate to promote the formation of galaxies and, eventually, all of the exciting things galaxies host: stars, dust, apple pie, etc.

Understanding the evolution of the galaxies in the universe since this period of initial formation is the subject of my research. The processes affecting this evolution (e.g., supernovae and super-massive black hole feedback, galaxy mergers, acquisition of cold gas from the local environment) are the key to understanding the formation of structure and energy transfer in the universe.

After I give warning that I must get a bit more technical, whomever I’m speaking with will usually hail the bartender and ask for another round.

Revolutions in the sciences often arise from properly categorizing items and discovering patterns. What was chemistry before Mendelev? Or biology before Linnaeus? This image was made by observing a small region of the sky (less than half the width of a full moon) for 100 orbits with the Hubble Space Telescope. It allows astrophysicists to observe approximately 95 percent of the universe’s history in a single frame, as it contains thousands of galaxies observed at diverse stages of evolution. It is apparent that some galaxies here are different in color and shape from others—but why? For decades we have linked morphology with the stellar composition of each of these galaxies, but the research I am conducting with Yonsei collaborators points to a need for a new classification scheme which incorporates mergers for understanding the fundamental physics which gives rise to the morphological diversity we observe throughout the universe.

My research is particularly focused on the analysis of early-type galaxies, or ETGs, which I observe at ultraviolet, or UV, wavelengths temporally near to the epoch of peak star formation in the universe. ETGs were once assumed to be, as a class, essentially “red and dead” — composed of old stellar populations too cool to emit strongly at UV wavelengths and severely deficient in recent star formation, the signpost of galaxy evolution. These galaxies, we thought, formed in the early universe, and had consumed most of the resources necessary for star formation when the universe was still relatively young. Now, they are like an old man, casually sipping a glass of sweet tea in his rocker recounting, for anyone who will listen, stories from “back when I was a young whippersnapper.”

If you recall what you learned of galaxies in your introductory astronomy course, you might wonder at this point, “In a universe replete with billions of galaxies that are currently evolving — colliding and merging, generating bursts of new stars as a result of this catastrophic reprocessing — why study these ‘red and dead’ ETGs to understand galactic evolution?” Taking a textbook definition at face value, you and my colleagues would be absolutely right to question why I have selected this class of galaxy for study.  The textbooks, however, are incorrect: The last decade of astrophysics research has redefined what it means to be an ETG.

Beginning in the 1980s and really taking off (pun intended!) in the 2000s, space-based observatories like the Hubble Space Telescope have confirmed that ETGs not only emit strongly in the UV (surprisingly from both young and old stellar populations), but also revealed that almost a third of these galaxies show evidence for recent star formation in the previous billion years.  Better yet, star formation in ETGs is unobscured by the manifold dynamic processes associated with stellar and galactic evolution (e.g., supernova, AGN feedback, affects of gas and dust distribution). Thus, ETGs provide (almost) pristine laboratories for the study of stellar and galactic evolution.

Currently, and for a very limited time because Hubble will be de-orbited in the next few years, I am continuing the study of these supposedly “dead” galaxies at ultraviolet wavelengths using the Wide Field Camera 3 on the Hubble Space Telescope.  This telescope combines ultraviolet sensitivity with Hubble’s unrivaled spatial resolution, allowing me to directly address fundamental questions about the evolution of galaxies in the universe.

“But Michael,” some ask, “the Hubble telescope is 550 kilometers above us in space; why did you have to do this exciting research here in Korea?”  The answer to that question begins with the GALEX observatory (still in Earth orbit) and ends here at Yonsei. Of the 13 institutions engaged specifically in scientific collaboration with the GALEX mission, a NASA Explorer-class UV observatory that was launched in 2003, Yonsei University researchers S.K. Yi and Y.W. Lee were the only international science collaborators.  Though a small telescope (Hubble’s collecting area is more than 20 times that of GALEX), observations of ETGs obtained with GALEX are largely responsible for motivating the scientific community to reconsider the traditional paradigm of galaxy formation. Fortunately for Yonsei, when Yi finished his posts abroad in Europe and the United States, he brought his expertise back to Korea and began to build a research group — Galaxy Evolution Meeting, or GEM — that is partly responsible for the recent international recognition Yonsei has earned from the community studying UV emission in galaxies and stellar objects. Fortunately for me, GEM members are specifically interested in many of the same topics I am considering in my dissertation research.

Observational astrophysics at UV wavelengths is an expensive endeavor (it must be space-based because of the Earth’s atmosphere’s opacity to UV photons), so UV missions are few and far between and data is limited. Thus, the community of UV astrophysicists is quite small and opportunities for direct collaboration for extended periods with members in the field are few.  Upon hearing about GEM, I knew I had to find a way to get to Yonsei to work with this group. When my adviser suggested the Fulbright program, I saw my opportunity.

During my term at Yonsei so far, we have made great progress through this new collaboration and the results are exciting.  We have confirmed that recent star-formation events have occurred in a significant minority (about 40 percent) of ETGs and we have addressed the mechanism(s) by which star formation was reactivated in these otherwise “quiescent” galaxies. This novel result will provide new observational clues, which will test the theoretical paradigm for the evolution of massive field galaxies.

Understanding the formation and evolution of these galaxies is fundamental to the study of the evolution of matter and energy in the universe for a number of reasons. First, galaxies contain much of the “normal matter” that makes up the atoms and their sub-atomic constituents on the Periodic Table.  But, this matter is merely an approximate 4 percent of the universe’s “mass-energy budget.”  Most of the energy budget of the universe is in the form of “exotic,” (exotic is a fancy word we scientists use when we don’t have a clue what it is) dark energy or (to a lesser extent) dark matter. Fortunately, dark matter does interact gravitationally, and we know that galaxies will form and grow in “dark matter halos” (i.e., local overdensities of this exotic “stuff”). Thus, galaxies can “trace” the distribution of this material. Furthermore, the formation of galaxies is dictated by cosmological “initial conditions” that are difficult, or impossible, to directly observe. By investigating these processes, we can better understand how matter and energy are distributed, and learn about the dynamics of that distribution over time, which, in turn, reveals the underlying physics of the universe that dictates how everything in the universe fundamentally “works.”

The United States’ research community could try and answer the questions all on our own but with the main question being “How does everything work?” I think we all would be better served in our endeavor by a team effort. The Fulbright program is helping, in its unique way, to develop these new partnerships. The collaborations which I have initiated here during my term will require years or decades to bear fruit, but the first steps — and real progress — have been made toward answering some of the most fundamental questions any human, American, Korean or otherwise, has ever been fortunate enough to ponder.

Michael Rutkowski is a 2011 Junior Researcher affiliated with the Department of Astronomy at Yonsei University.