Texas A&M Astronomer Explores Connection Between Supermassive Black Holes and Their Home Galaxies

Texas A&M University astronomer Jonelle Walsh doesn’t sugar-coat things regarding science’s understanding of the mysterious cosmic phenomenon known as supermassive black holes.

“There’s simply a lot we don’t know,” Walsh said, with emphasis on the “a lot” part.

Walsh, however, is not one to shy away from a challenge. As a Texas A&M Mitchell Institute Postdoctoral Fellow in Astronomy who’s only six years removed from receiving her Ph.D. at the University of California, Irvine in 2011, she is the principal investigator of a 30-member international collaboration — not to mention the only representative from Texas A&M — that is examining the correlation between supermassive black holes and the galaxies in which they exist.

Walsh’s study is part of the Gemini Observatory’s Large and Long Program, which grants extra observation hours to high-impact projects.

According to the Gemini Observatory’s official website, the extended observation period is intended to provide a greater flexibility for research and “promote collaborations across the partnership’s communities.” Walsh and her team are conducting their research at the 8.1-meter Gemini North telescope situated near the summit of Mauna Kea in Hilo, Hawaii, where they have been allocated 253 observing hours over the next three years.

“Our Gemini Large and Long Program is aimed at trying to understand the connection between black holes and galaxies by studying a wide variety of galaxies,” Walsh said. “Currently, the easiest galaxies to observe and model have been studied, but they are not representative of the nearby galaxy population. Therefore, our understanding of the interplay between black holes and their host galaxies, and our interpretation of how they grow and evolve together, could be biased.

“I think there’s a real niche here for Gemini to be able to make an impact on the field of supermassive black holes. I’m just really excited about it. I think we can do some really interesting science, and there is a lot to learn.”

Before joining the George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy in fall 2014, Walsh spent three years as a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellow at The University of Texas at Austin. Her research focuses on measuring the masses of black holes via stellar and gas-dynamical methods using high-performance computing resources and observations from high angular resolution facilities, including the Gemini and Keck telescopes, the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array.

Supermassive black holes are the largest type of black hole. Like the more common stellar-mass black holes, supermassive black holes have existed since the infancy of the universe, some 800 million years after the Big Bang. Their gravitational pull is so powerful, not even light can escape.

Stellar-mass black holes are believed to form when the center of an immense star collapses upon itself at the end of its life and compresses into an incredibly dense matter. Supermassive black holes, on the other hand, contain between a million and a billion times more mass and are found at the center of almost every known galaxy. How these galactic behemoths were able to get so huge so relatively soon after the formation of the universe is a question that has stumped scientists for decades.

Walsh says that, based on previous studies, the size of supermassive black holes seems to be interdependent on the galaxy in which it resides, suggesting that they somehow grow together.

“There is a chicken and egg problem,” Walsh said. “Did the black hole come first and the galaxy grew around it, or did the galaxy come first and a black hole formed at the center? Or maybe, somehow, both objects formed together and have been growing in lock-step with one another over time. That’s one of the questions I’m interested in eventually answering.”

Walsh’s group plans to observe the black holes of 30 different galaxies during the next three years. By measuring the speed and motion of nearby orbiting stars, the team can construct dynamical models in order to infer the mass of each black hole. It’s a two-step process that fittingly begins in Texas — specifically, with the telescopes at The University of Texas at Austin McDonald Observatory, which Walsh uses to analyze the outer galaxy parts. Once that phase is complete, she looks to the Gemini North telescope and similar 8-to-10-meter-class telescopes to measure the inner parts, where the so-called “sphere of Influence” of the black hole is.

An integral feature of the Gemini North telescope that Walsh’s team will be taking advantage of is its ALTitude conjugate Adaptive optics for InfraRed (ALTAIR) system, which is capable of correcting image distortions caused by the Earth’s atmosphere to produce high-resolution data.

“The Gemini observations are really important for probing the innermost regions of galaxies,” Walsh said. “We can obtain very sharp images; it’s almost like observing from space. Because Gemini is also a very large telescope, it allows us to collect a lot of light at the same time so that we can target objects that are pretty faint. ”

Despite the fact that her Large and Long project is in the early stages, Walsh predicts the quality and sheer volume of data they obtain at the end of three years will require several more years of analysis.

“We’re really pushing the boundaries of what we can do observationally and with the modeling,” Walsh said. “At the end of three years, hopefully we can have a more complete census of the local black holes. We just want to gain a more fundamental understanding of how black hole masses and galaxies are connected.”

For more information about Walsh’s study, Addressing a Bias in the Relation Between Galaxies and Their Central Black Holes, visit http://www.gemini.edu/node/12610

Learn more about Walsh and her research as well as Texas A&M Astronomy Research Group.

# # # # # # # # # #

About Research at Texas A&M University: As one of the world’s leading research institutions, Texas A&M is at the forefront in making significant contributions to scholarship and discovery, including that of science and technology. Research conducted at Texas A&M represented annual expenditures of more than $892.7 million in fiscal year 2016. Texas A&M ranked in the top 20 of the National Science Foundation’s Higher Education Research and Development survey (2015), based on expenditures of more than $866.6 million in fiscal year 2015. Texas A&M’s research creates new knowledge that provides basic, fundamental and applied contributions resulting, in many cases, in economic benefits to the state, nation and world. To learn more, visit http://research.tamu.edu.

-aTm-

Contact: Chris Jarvis, (979) 845-7246 or cjarvis@science.tamu.edu or Dr. Jonelle Walsh, (979) 845-7778 or walsh@physics.tamu.edu