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Do Supermassive Black Holes Fuel the Evolution of Galaxies?

Thaisa Storchi Bergmann

Thaisa Storchi Bergmann delivers a topical lecture at the 2016 AAAS Annual Meeting on supermassive black holes. | Boston Atlantic Photography

Scientists studying the supermassive black holes are learning more about how these phenomena control the growth of the galaxies that surround them, said Thaisa Storchi Bergmann at the 2016 AAAS Annual Meeting.

In her 12 February topical lecture, Bergmann, a professor of physics and astronomy at the Federal University of Rio Grande do Sul, shared a short history of how astronomers’ conceptions of black holes have changed since the time of Einstein, with data from her own recent observations of supermassive black holes.

Supermassive black holes, which can be hundreds of thousands to billions of times more massive than the sun, may be found at the center of most galaxies. No light escapes from these regions, and astrophysicists like Bergmann must instead study the traces of gas, dust, and the piercing jets of plasma that are sometimes found in their vicinity.

In many cases, astronomers are studying the light and other electromagnetic waves—including X-rays and gamma rays—from events that occurred billions of years ago and whose emissions are just now making their way to earth.

“In some ways, we are the archaeologists of the universe,” Bergmann said.

Bergmann studies accretion disks, the diffuse cloud of matter that is drawn into orbit by the powerful gravity of a supermassive black hole before being disappearing into it completely. She shared some of her first observations of how these accretion disks operate in brilliant active galactic nuclei, or AGNs. AGNs are the highly luminous, compact regions near the center of some galaxies.

Bergmann and her colleagues studied the way matter in an accretion disk moves in its “death spiral” near the AGN of the galaxy NGC1097, a spiral galaxy about 45 million light years away from Earth. The orbiting motion of the accretion disk can trace the “death spiral” of its matter as it falls into the darkness of what the astrophysicists measure to be a supermassive black hole.

But this death may be a productive one, Bergmann said. As matter falls into the black hole, it can generate powerful jets of energy. She compared the process to a hydroelectric power plant.

“It’s like you have water falling in a dam, and then the water will move a turbine and then generate electricity,” Bergmann said. In this case, matter falling into the black hole is water over the dam, she explained, and the turbine is the accretion disk.

Now, Bergmann and her colleagues continue to take a closer look at how AGNs and their supermassive black holes fuel the shape and size of a galaxy throughout its lifetime.

Bergmann is a 2015 recipient of the L’Oréal-UNESCO For Women in Science International Award, and does much of her research at the Gemini telescope observatory in Chile.


Becky Ham

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