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May 30, 2013

Megan Donahue: Galaxy quest

May 30, 2013

Megan Donahue is a professor of physics and astronomy and an expert in galaxies and galaxy clusters. She is interested in cluster evolution, not only in finding clusters but also in how they're found. She studies the ecology of the cluster systems—the gas between the galaxies, how it falls into galaxies and makes stars and feeds black holes, and how that gas changes in its chemical make-up over time.

Did you ever wonder how NASA decides what to do with the Hubble Space Telescope? It orbits the Earth once every 90 minutes, and it conducts approximately 200 scientific programs over the course of a year. To be one of those programs, a scientist has to write a proposal. About 1,000 proposals are received each year.

A few years ago, I joined a proposal team answering an unusual call for "multi-year" proposals. Marc Postman of the Space Telescope Science Institute assembled the team of experts, Mission-Impossible style, to propose a project to get unprecedented observations of some of the most massive clusters of galaxies in the universe. I was stunned and amazed when we were awarded about 750 hours of time to work on our project over three years. We just completed our final observation in the last month. We called our program "CLASH," in part because we are fans of the band the Clash, but also to represent "Cluster Lensing and Supernovae with HST." Yeah, it's a stretch, but…did I mention London Calling really rocks?

One of the really cool things that happened in the last year is that we discovered two of the most distant galaxies ever identified by humans. These galaxies are so far away that their light has been traveling for more than 13 billion years; we are seeing these galaxies as they were only about 400 million years after the Big Bang. One implication of these discoveries is that the universe gets to the business of making stars really fast—it doesn't mess around.

One of the things that I really enjoy about working with a multi-national team is that everyone is really enthusiastic, supportive of each other, and every one of them is working hard to learn as much as we can from this hard-won data. We are acutely aware that the Hubble Space Telescope will not last forever, and is unlikely to ever do a project like ours again, so we were under pressure to design a program that could be used to answer many scientific questions. The images that we are creating from the data are simply beautiful.

A day in the life of a CLASH investigator (me) usually starts with me checking my email. My European colleagues have been awake for hours; my Taiwanese colleagues went to sleep hours after I did. By checking email I can catch up on the latest questions, comments and even drafts of papers and new proposals. I will answer any questions that fall into my area. I download and read the new proposals and paper drafts. I like to make comments in PDF documents, and then send that back to the authors. Then I settle down to my own analysis projects, which usually involve (in various degrees) downloading data from the team websites, writing data analysis programs and analyzing the data.  

I have two graduate students, Aaron Hoffer and Tom Connor, working on various aspects of the research. Aaron analyzes our X-ray observations and Tom has been studying the light from the cluster galaxies detected by Hubble. They have also been using the SOAR telescope to collect spectroscopy of galaxies for even more information about them.

Occasionally I've had to write proposals for follow-up programs, and that often takes a week or two of very intense collaborative work. Coincidentally, we were very excited just to hear on May 30 that some of our follow-up projects have been successful in getting more of that precious Hubble observing time!

We have a weekly telecon (at least) to talk to each other live (a real trick with time zones spanning Taiwan, the U.S. West and East coast, Europe and Israel). Once a year, in the last three years, we have met up in Europe where many of our collaborators live. Most recently, we met in Balboa, Spain, which is a beautiful city with a famous art museum called the Guggenheim that reminded me of our new museum on campus, architecturally outrageous—but awesome. I think it would be really cool to have an exhibit of Hubble pictures in MSU's Broad Art Museum, just putting that out there. 

Read more about Donahue’s work>>

Learn more about CLASH>>

Infant galaxy offers peek at early universe>>