Annual Report [2018]

Kavli Summer Program in Astrophysics

Flatiron Institute

International collaboration, swirling galaxies and an exploding steam pipe all defined summer 2018 for attendees of the Kavli Summer Program in Astrophysics, hosted at the Flatiron Institute’s Center for Computational Astrophysics (CCA).

Over six weeks, 17 graduate students participated in this annual learning and research opportunity that connects students with senior-scientist mentors. The students listened to lectures from experts in the field and worked on research projects that yielded significant discoveries. Participants formed strong bonds, with a diverse group of graduate students, postdoctoral researchers and established faculty members coming together in the spirit of collaboration and scientific discovery.

“Afterwards, we had so much positive feedback from both students and mentors about how invigorating it was and how much they learned,” says Greg Bryan. He and Rachel Somerville co-directed the Kavli program and co-lead the CCA’s galaxy-formation group. “It was a chance for some of the best students, postdocs and faculty to come together and forge ties, learn about the field as a whole and make real contributions,” he says.

The program launched in 2010, with the Kavli Foundation serving as its principal sponsor since 2016. The event’s founding director, Pascale Garaud, is professor of applied mathematics at the University of California, Santa Cruz. She modeled the program on one she attended as a graduate student at the Woods Hole Oceanographic Institution in Massachusetts. “That program changed my career, and it changed me on a personal level,” Garaud says. “I decided I wanted to do something similar for students in astrophysical sciences.”

Hosting duties for the summer program alternate between the University of California, Santa Cruz and other institutions around the world. CCA director David Spergel embraced the idea of bringing the event to the Flatiron Institute, as both the program and the institute emphasize the importance of collaboration.

The 2018 program focused on how galaxies form and evolve, though not all the participants have backgrounds in galaxy formation. “Many of the graduate students come from institutions where this subfield is not well-represented, so they might not have had much opportunity to study or do research on this topic,” Somerville says.

After a week of lectures on galaxy formation, students partnered with mentors and began working on research projects, the goal being for students to report their results in a peer-reviewed journal.

A density map of the gas in and around Althaea, an early-universe galaxy simulated by Daisy Leung and colleagues. The gas has dense knots and clumps, shown in orange and red. These structures are the birthplaces of young stars and affect the subsequent evolution of galaxies to the present day. Image courtesy of Daisy Leung

“It’s one thing to read some papers and do some analysis yourself; it’s another thing for someone to teach you firsthand,” says graduate student Corey Brummel-Smith of the Georgia Institute of Technology in Atlanta.

Graduate student Daisy Leung modeled the emergence of the earliest galaxies in the universe. As a trained observational astronomer, she appreciated the opportunity to work with theorists and further hone her computational skills. “The field can only make progress if observers are talking to theorists,” says Leung, who studied at Cornell University and is continuing her thesis work at the CCA. Her work simulated the small- and large-scale physics that govern how clouds of molecules collapse and evolve to form galaxies. The results provide predictions that future surveys, such as those using the James Webb Space Telescope, can test.

For his project, Yale University graduate student Darryl Seligman explored interactions between gas and dust in space. An outstanding question for astrophysicists is how dust specks coalesce to form an Earth-sized rocky planet. Clusters bigger than a poppy seed shatter when they crash into each other, rather than sticking together. Seligman numerically simulated the long-term evolution of these interactions. Dust faces a headwind as it passes through gas. The dust particles then behave like cyclists in a race, huddling together to minimize drag and creating clusters. Seligman’s simulations showed that the presence of a magnetic field causes the dust to bundle together into sheet-like clumps that might gently combine to form the building blocks of a planet. The results offer insights into the behavior of the dust and gas that surrounds a black hole or that inhabits the void between a galaxy’s stars.

Alexander Kaurov (left), a postdoc at the Institute for Advanced Study in Princeton, New Jersey, chats with graduate student Daisy Leung (right) during the Kavli Summer Program in Astrophysics.

Other projects included how behemoth black holes squelch star formation in galaxies and comparing models of galaxy assembly with real observations. Even though each student had his or her own project, everyone rallied to help one another. “There was no sense of competition except for against the clock,” Bryan says. 

“The event was a far more fruitful experience than having 17 projects at 17 different institutions.”

That teamwork was tested on the Thursday before the final week of the program. In the early morning, a steam pipe exploded outside the Flatiron Institute, leaving the building inaccessible for more than a week. Students who had left their laptops inside overnight found themselves computerless and panicking about not being able to complete their projects.

Eventually, the program relocated to New York University’s physics department, which graciously offered space for everyone to work. The Flatiron Institute’s Scientific Computing Core procured loaner laptops so that students could finish their research in time. “It looked like Christmas Day,” as everyone unboxed their computers, Leung recalls.

“They were the exact feelings I hoped people would get out of the program — that feeling of finding a family.”

The experience, although trying, brought the group together, Seligman says. “It felt like an academic family.”

On the program’s final day, after the students presented their results, Leung gave one final presentation on behalf of all the students. She outlined how the summer program and the CCA had inspirited her and others to go forth in science and how much the collaborative and diverse environment meant to them.

“They were the exact feelings I hoped people would get out of the program — that feeling of finding a family,” Garaud says. “It’s going to be hard for any other host institution to top what CCA did.”

The event was such a success that the CCA will host its own, separate summer program for graduate students in 2019, with a focus on black holes, neutron stars and other compact objects. “This is an opportunity to bring people together and encourage the next generation of scientists,” Somerville says.