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College of Science and Mathematics

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Are Black Holes the Chicken or the Egg?

November 19, 2013

Contact: Vardha N. Bennert
805-756-7317; vbennert@calpoly.edu

Cal Poly faculty and students at the Lick Observatory.

(Left to right) Anna Pancoast, Vardha Bennert, Bryan Scott and Kelsi Flatland
at the Lick Observatory near San Jose, January 2013

Which came first, the galaxy or the black hole? Physics Professor Vardha N. Bennert and her students will investigate that question with a $300,000 grant from the National Science Foundation.

Virtually all the galaxies for which astrophysicists have collected and analyzed data have black holes at their centers. As the scientific community has studied these black holes, it has found a consistent relationship between the mass of a black hole and the mass of its host galaxy, which suggests that as one forms and grows, it causes the other to form and grow. But which one started the whole thing?

Bennert and her students will try to find out using data collected by the Hubble Space Telescope. The astrophysicists will estimate the mass of galaxies 10 billion light-years away as well as their corresponding black holes. "Because they're so far away, we're looking back in time because it took the light so long to reach us," Bennert said.

The researchers will then compare the mass of these distant galaxies and black holes to the mass of their counterparts in relatively nearby, active galaxies, that is, galaxies that have a black hole in their center that is currently growing. Whichever distant body is more massive than expected based on the data for active galaxies likely came first.

Bennert was awarded observing time at the world's largest optical telescopes, the 10-meter Keck telescope in Hawaii, thanks to her collaboration with an international team of astrophysicists, including Tommaso Treu, a physics professor at University of California, Santa Barbara. While Bennert observes active galaxies using the Keck telescope, her student-researchers join her remotely and then analyze the spectra she collects to determine the mass of the black holes. "The students are involved in forefront research," Bennert said.

Students also participate in observing runs at the Lick Observatory near San Jose where they get real-world experience using a large telescope. "They get trained in the afternoon and operate the instrument, and I just watch to make sure they do it right. After a couple of nights, they just take over. It can't be more hands-on," Bennert said.

Bryan Scott, a physics student, has done observations at Lick and joined Bennert remotely at Keck. "I think research changes how you think about the world," he said. "Research integrates skills that you don't get in classes and uses them to solve problems in non-obvious ways."

Scott recently presented the group's research results at the regional American Physical Society meeting at Sonoma State University and will travel to Washington, D.C., to make a similar presentation in January 2014 at the annual American Astronomical Society meeting. Commenting on his experience at the conference, Scott said, "Aside from a chance to share and receive feedback about my work from other physicists, I am also exposed to the work that people are doing in many fields. It helps to make you feel like a contributing member of the community."

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