Galaxy Research Earns Astronomer CAREER Award

The NSF Faculty Early Career Development (CAREER) Program has awarded $681,439 to IU Department of Astronomy assistant professor Katherine Rhode to enhance her research on globular clusters over the next five years.

Globular clusters are luminous, massive swarms of hundreds of thousands of stars that can number in the hundreds, or even thousands, within galaxies. They are of special interest because a system of globular clusters in a specific galaxy can provide a fossil record of the conditions present in that galaxy when the clusters formed billions of years earlier.

Rhode said the funding will allow her to begin a multi-year, wide-field imaging survey of globular cluster systems in giant galaxies found as far as 65 million light years away.

“The goal is to quantify the properties – the numbers, spatial distribution, chemical compositions – of the globular clusters in the galaxies and use these properties to test theories for how the galaxies formed,” she said. “Such a survey is a huge effort and will involve lots of planning and preparation, followed by years of observations and data analysis. So a five-year award like this enables me to initiate and carry out the type of big survey that will have more of an impact in the field than a few shorter-term studies.”

Rhode plans to use the WIYN 3.5-meter telescope at Kitt Peak National Observatory near Tucson, Ariz., a facility owned in partnership between IU, University of Wisconsin, Yale University and the National Optical Astronomy Observatory, to conduct the survey. She said plans also include use of the One Degree Imager (ODI), a $10 million camera currently being installed on the WIYN telescope designed to correct for atmospheric blur that can occur across the telescope's wide field of view.

The WIYN ODI has a one-degree-across field of view, extremely wide at about twice the diameter of the moon or about 100 times larger than the field of view of the Hubble telescope, which will allow Rhode to observe the entire globular cluster system of each galaxy, or even a few galaxies at a time, in a single pointing. Another advantage of the ODI is its very high resolution, which helps astronomers distinguish real globular clusters from contaminating objects such as faint, distant galaxies.

The velocities of the clusters moving around their host galaxies will also be measurable by studying the clusters' spectrum of electromagnetic radiation, which in turn will provide information about the distribution of mass in the galaxies and allow for the study of the galaxies’ dark matter haloes.

In 2007 Rhode and colleagues discovered the first clear case of a black hole in a globular cluster, and with the new survey data expected to be collected as a result of the CAREER award, she hopes to find and study more black holes that exist in these unique star clusters.

Storing ODI images the size of one billion pixels and four gigabytes each is another challenge Rhode has already been working on with the assistance of a $74,994 IU Faculty Research Support Program award, and she's enlisted the assistance of University Information Technology Services (UITS), IU's Data Capacitor and the Massive Data Storage Service and its 4.2 petabyte capacity. The system that Rhode and UITS staff envision would allow for the reduction, analysis and archiving of ODI images.

“If we are successful at producing this system for analyzing and storing gigapixel images, I anticipate that IU Astronomy and IU UITS will gain much broader recognition in the astronomical community, and perhaps the larger scientific community,” Rhode said. “So it will, we hope, open up ODI to a broader community of users and help the instrument have an even greater scientific impact.”

Rhode received a B.A. in physics from Sonoma State University in 1989 and then held positions at the Maria Mitchell Observatory, NASA-Goddard Space Flight Center and the Harvard-Smithsonian Center for Astrophysics before earning an M.A. in astronomy at Wesleyan University in 1997. She was awarded a Ph.D. in astronomy from Yale University in 2003 and then was an NSF Astronomy & Astrophysics Postdoctoral Fellow with a joint appointment at Wesleyan and Yale Universities through 2006. She came to the IU College of Arts and Sciences' Department of Astronomy in August 2007.