BOZEMAN – A long time ago in galaxies millions to billions of light years away, gas and dust particles were ejected from their orbits around black holes and hurtled into space.

Later, on 21st century Earth, those particles’ optical wavelength emissions were picked up by a powerful telescope, recorded in an astronomical data bank and then analyzed by a Montana State University graduate student looking for the “smallest of supermassive black holes” in the universe – that is, those with masses around a million times that of our sun.

Through that analysis, Sheyda Salehirad identified 388 previously undiscovered small, low-mass galaxies, which are believed to harbor black holes smaller than those found in larger, high-mass galaxies. The fifth-year doctoral student in MSU’s Department of Physics in the College of Letters and Science was even more excited when she discovered that 70 of them are even smaller “dwarf galaxies” that potentially host yet smaller black holes, the study of which may provide scientists with significant insight into still-unanswered questions about how supermassive black holes form.

The results of Salehirad’s study have been accepted for publication in The Astrophysical Journal. Her paper is the first of its kind to extend such searches to southern sky regions, where she discovered some of the 388 far-distant, low-mass galaxies harboring supermassive black holes.

Astronomers categorize the mass of galaxies in terms of solar mass – that is, their masses compared to that of the sun. Small, low-mass galaxies are believed to harbor smaller black holes.

Scientists don’t know what “seeded,” or initiated, the first supermassive black holes, and they believe they are unlikely to make that discovery by studying existing supermassive black holes in massive galaxies. That’s because supermassive black holes grow over time, mostly by feeding on gases funneled down to them during the mergers of galaxies or by merging with one another, which also can happen when galaxies merge. Those processes likely obliterate clues about the origins of supermassive black holes, and so scientists believe studying smaller black holes in low-mass galaxies with quieter merger histories could uncover clues about the seeds of supermassive black holes.

“Some studies show that if we look at smaller galaxies that harbor black holes, we can understand how the seeds start,” Salehirad said. “The goal of our work is to observe as many dwarf galaxies that harbor active black holes as we can find, determine their masses and inform seed models.”

Her academic adviser, Amy Reines, assistant professor in the Department of Physics who studies dwarf galaxies and active black holes, said the results of the study are significant.

"Sheyda’s results are extremely exciting because these little galaxies hold clues to the origin of the first supermassive black hole ‘seeds’ in the early universe,” Reines said. “This work is also important for our understanding of how galaxies and black holes evolved together."

Salehirad met Reines while searching for a doctoral program in which she could further her study of gravity, the primary focus of her master’s studies in Minnesota. She visited Montana State because of its eXtreme Gravity Institute and quickly became interested in Reines’ work.

“She’s a very renowned person in her field,” said Salehirad of Reines. “It’s been a privilege working with her.”

Salehirad expects her findings to help scientists narrow the scope of possibilities about the origins of supermassive black holes until even more data become available. She said the James Webb Space Telescope “is going to change the game because it will provide data in other wavelength ranges” than the optical spectrum, but added, “until then, it’s important to make use of what we have.”

“It’s great to find something you’re looking for,” she said. “Discovery is always fun.”

- by Diana Setterberg, MSU News Service -

More From K96 FM