Physics and Astronomy Students Explore Behavior of Supermassive Black Holes in Different Environments in Space

Oct. 9, 2024

By Stephanie Godward, Communications and Marketing Director, College of Arts and Sciences

Divya Patel and Clayton Robertson are examining the behaviors and many remaining mysteries of supermassive black holes, with research that continues to explore answers to questions about these violent and still largely unknown aspects of space.

“My research is focused on Active Galactic Nuclei (AGNs), where supermassive black holes reside, and they get active by consuming dust, spewing out light and radiation in the form of jets. We can then analyze the light to understand more about AGNs, their formation, and their place in the galaxies,” Patel said.

Patel, a junior majoring in astrophysics with a minor in mathematics, worked with Robertson, a PhD student studying astrophysics. Robertson graduated with degrees in physics and mathematics before pursuing his PhD, and served as a mentor for Patel through the Summer Research Opportunity Program. This research also was funded by the Mentored Undergraduate Research and Creative Activities Grant funding from the College of Arts & Sciences in 2023-2024.

“I have always been interested in black holes ever since I was in high school, and it’s been about 100 or so years since we first found out about black holes. It’s still interesting how much we do not know, what happens in singularity; so, it’s fascinating to study and understand more about black holes by studying AGNs,” Patel said.

AGNs are home to supermassive black holes that are extremely active, shooting out huge amounts of matter into space. Scientists and students study how they behave by using Baldwin-Philips-Terlevich (BPT) diagrams, which look at the ratios of light emitted by these objects. Patel and Robertson utilized the GAMA survey obtained from Australian and British telescopes, then analyzed the data using Python and other software.

When scientists and students like Patel and Robertson observe the universe, they see three main areas or regions in space: filaments, tendrils, and voids. Filaments are massive structures filled with galaxies. Tendrils form from these filaments, while voids are empty regions with very few, if any, galaxies. Patel and Robertson’s research examined AGN behavior in these three different galactic regions in order to answer this question: do AGNs decrease as we move away from filaments due to reduced gravitational activity?

Roberston noted the intriguing nature of voids in space, like the Bootes Void, which are vast areas with almost nothing in them. This emptiness is puzzling because it seems like there should be something there, making these voids fascinating to study.

“What we are looking at are AGNs in that space and seeing if there is a correlation. Do AGNs almost like being around each other, and therefore they can eat up more gas from each other? And is the gravitational interaction from each galaxy pulling each other there, and would that say a lot about the kind of dust distribution and the kinds of things going on in the galaxy compared to being in a void space where there is nothing around?” Robertson said. “If there’s nothing around, how does an AGN thrive? That’s the cool thing about AGNs – they need a lot of stuff. These big black holes need food, they need dust to thrive, so what happens when you’re in void space with not as much stuff to feed on?”

Patel and Robertson ultimately found that the percentage of AGNs increases as you move from void regions to filament regions, which could be due to gravitational forces linked to these structures.

Additionally, they found that the number of AGNs decreases as you get farther away from the filaments and into the void regions.

“We were not expecting to find any AGNs in void galaxies, because there is not a lot of gravitational interaction between galaxies, because void space is mostly empty. But we did find AGNs there; not a lot, compared to filaments, but we did find some, so we are interested now to see what kind of galaxies are residing in those void spaces,” Patel said.

Patel said the findings help us to understand how AGNs are spread out and behave in different parts of the galaxy.

“Do AGNs need buddies to thrive? We found that yes, they probably do, and that has a lot to do with the interactions, because the gravity interactions are maybe pulling them together more, and so we are trying to see how they behave in each environment,” Robertson said. “When we find AGNs in void galaxies, what’s keeping them going? What's keeping the supermassive black hole fed?”

Benne Holwerda, professor of physics and astronomy, said Patel is now fantastically positioned to be accepted into graduate school and to pursue his career aspirations, and said this research will also help scientists to understand more about how galaxies form and evolve.

“Doing research is a creative endeavor; a very measured creative endeavor that we get excited about,” Holwerda said. “We are still trying to understand the actual role of AGNs in how galaxies evolve. The supermassive black hole sits in an area that is the size of our solar system. It's tiny compared to its host galaxy and tinier still compared to the larger environment. Yet, if it switches on, it blows out gas at such speeds and temperatures that it can make a cocoon of hot gas around galaxies and switch on a flow of gas into it, switching off star formation. As we understand it, AGNs stop their galaxies from forming new stars, so they become dead. That is our mechanism, but we still don’t understand how it works. I am curious to see if we will answer more questions.”

Their exploration of inquiry continues this semester and beyond as they embark on the research equivalent of “bar hopping,” as Robertson said — examining whether galaxies with bars are more likely to host AGNs. A barred spiral galaxy is one with a central, bar-shaped structure made of stars. They want to determine if there's a correlation between the presence of a bar in a spiral galaxy and the likelihood of finding an AGN. To do this, they will analyze both the galaxy's environment and whether it has a bar, using data from the Galaxy Zoo project, where volunteers have identified barred galaxies.

Patel looks forward to exploring answers to more questions, including: why do galaxies have AGNs – and where do you find them?

“My next step will be finding what kinds of galaxies are lying in void space with AGNs in them, and see what kind of galaxies have AGNs in filaments and tendrils as well,” he said.