Laura DeGroot, assistant professor of physics at The College of Wooster, and alumni Karmella Buttler ’25 and Taliah Lansing ’25, along with a collaborator at NASA, share their findings on galaxy evolution using data from the James Webb Space Telescope. By studying galaxies at cosmic noon, when star formation in the universe was at its peak about 10 to 11 billion years ago, the researchers investigated whether disk galaxies are growing from the inside out. In “Quantifying the inside-out formation of disk galaxies at 1.5 <= z <= 3.0” currently available here and awaiting peer review in the Astrophysical Journal, DeGroot and her collaborators report on evidence they’ve found that supports the inside-out growth of disk galaxies, which are flattened, circular groups of stars and gases that include spiral galaxies like the Milky Way. This latest research suggests that these galaxies grow in size by adding new stars to the outskirts of the already-established stellar populations.
“The Webb telescope is providing unprecedented detail of galaxies, enabling us to study galaxy morphology like never before,” said DeGroot. “We’re able to push the boundaries to further distances and with finer detail to better understand how galaxies evolve with time.”
DeGroot has long studied the shape, structure, and classification of galaxies with her collaborator, Swara Ravindarnath, deputy chief scientist for NASA’s Cosmic Origins program. Their partnership began when DeGroot was a graduate student at University of California, Riverside. “When recent work using data from the Hubble Space Telescope indicated that inside-out disk growth may be incorrect and could be completely accounted for due to dust, we thought we could use the higher-resolution capabilities of the James Webb Space Telescope to challenge these results and see whether we reached the same conclusions,” DeGroot explained.
Although the new findings support inside-out growth, DeGroot emphasized that the field remains wide open. “Galaxy evolution is nowhere near solved,” she said, “so any additional information we have about how galaxies build up their mass is important.”
The research has been shaped in meaningful ways by student contributions. Physics major Buttler worked with DeGroot through the Wooster Physics National Science Foundation Research Experience for Undergraduates in 2022 and continued as a sophomore research student in 2022–2023. After only her first year, Buttler quickly mastered the background she needed in astrophysics and Python, a popular programming language, to explore different methods of analyzing the galaxies. She helped determine how best to remove galaxies with imaging issues before analysis and contributed to a new component of the project: examining how the colors of galaxies change from the inside outward to determine the effects of dust and inside-out growth. This work will be included in future publications.
Buttler, who is now a physics tutor at Stark State College in Canton, Ohio, enjoyed the independent research experience at Wooster because, she said, “I was given a lot of freedom to solve problems on my own and come up with creative solutions.” Discovering that computational physics was “deeply satisfying” made the project especially meaningful. “Much of my work involved constant iteration and debugging of our code, and despite that process being time-consuming, it was incredibly fulfilling for the challenge it gave,” she shared. “I enjoyed the research not only because programming was engaging but also because the research itself dealt with big questions about how the beautifully organized and massive galaxies we see today came to be.”
Lansing, now an ensign in the U.S. Navy serving as an instructor at its Nuclear Power School, joined the project as a sophomore research student in fall 2022. “The first time I saw the photo that served as our data set,” she recalled, “I couldn’t believe how many incredible things could be captured in one image. Factually, I knew there were a trillion galaxies in the universe, but that’s hard to conceptualize. Everywhere you looked in this photo was something new to discover.”
The physics and mathematics double major significantly accelerated the team’s ability to analyze galaxies using GALFIT, a program used to analyze galaxy images. By consulting with computer science faculty and identifying the most effective way to run GALFIT in Python, Lansing drastically improved the efficiency of analyzing large samples. Her work enabled the team to process data at a scale necessary for the current publication.
“Although I did not pursue a career in astronomy,” Lansing added, “this research made me a better scientist and learner. I’m grateful to have been a part of it.”
The project continues to expand thanks to contributions by current Wooster students. Akshit Deshpande ’26, physics major, has been working on finding the best methods for identifying disk galaxies, research that will help refine future samples used to study inside-out disk formation. Meanwhile, Anthony Gomes ’26, also earning his degree in physics, is investigating clumpy galaxies, young galaxies with abundant star formation that appear frequently in the team’s current dataset and have become part of DeGroot’s broader analysis. She also will be including future Wooster students as the next phase of the project unfolds.