Reviewed by Alex SmithAug 18 2021
A new high-powered simulation suggests that the spiral arms of the galaxies are accountable for drawing gas to energize their central supermassive black holes.
Claude-André Faucher-Giguère. Image Credit: Northwestern University.
The simulation demonstrated at Northwestern University is the first to clearly explain the process of gas flow all around the universe leading to the center of the supermassive black hole. Other simulations have already modeled the growth of black holes, but this is the first single computer simulation strong enough to provide detailed information of several forces and factors that act into the evolution of supermassive black holes.
Furthermore, the simulation provides rare information about the mysterious nature of quasars that are greatly luminous and fast-growing black holes. Quasars are among some of the brightest objects in the universe which often outshine the full galaxies.
The light we observe from distant quasars is powered as gas falls into supermassive black holes and gets heated up in the process. Our simulations show that galaxy structures, such as spiral arms, use gravitational forces to ‘put the brakes on’ gas that would otherwise orbit galaxy centers forever. This breaking mechanism enables the gas to instead fall into black holes and the gravitational brakes, or torques, are strong enough to explain the quasars that we observe.
Claude-André Faucher-Giguère, Study Senior Author and Astrophysicist, Northwestern University
The study was published in the Astrophysical Journal on August 17th, 2021.
Faucher-Giguère is an associate professor of physics and astronomy working at Northwestern’s Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Daniel Anglés-Alcázar is an assistant professor at the University of Connecticut and former CIERA fellow in Faucher-Giguère’s group and the first author of the paper.
Supermassive black holes are similar to the mass of millions or even billions of Sun and are capable of swallowing 10 times the mass of a Sun in just a year. However, while some supermassive black holes avail a consistent supply of food, others tend to fade out for millions of years and get reactivated rapidly with a serendipitous influx of gas.
For a long time, the factors about the process of gas flow throughout the universe to feed supermassive black holes were not explained.
To answer this question, the researchers designed the new simulation, which includes many of the important physical processes, such as the expansion of the universe and the galactic environment on a huge scale, gravity gas hydrodynamics and feedback from massive stars, into a single model.
Powerful events such as supernovae inject a lot of energy into the surrounding medium, and this influences how the galaxy evolves. So we need to incorporate all of these details and physical processes to capture an accurate picture.
Daniel Anglés-Alcázar, Assistant Professor, University of Connecticut
Developing on the earlier work from the FIRE (“Feedback In Realistic Environments”) project, the new technology immensely raises the model resolution and enables for following the gas as it flows throughout the galaxy providing over 1000 times better resolution compared to what was possible earlier.
“Other models can tell you a lot of details about what’s happening very close to the black hole, but they don’t contain information about what the rest of the galaxy is doing or even less about what the environment around the galaxy is doing. It turns out, it is very important to connect all these processes at the same time,” stated Anglés-Alcázar.
The very existence of supermassive black holes is quite amazing, yet there is no consensus on how they formed. The reason supermassive black holes are so difficult to explain is that forming them requires cramming a huge amount of matter into a tiny space.
Claude-André Faucher-Giguère, Study Senior Author and Astrophysicist, Northwestern University
“How does the universe manage to do that? Until now, theorists developed explanations relying on patching together different ideas for how matter in galaxies gets crammed into the innermost one millionth of a galaxy’s size,” Faucher-Giguère added.
The new simulations finally enable the researchers to model the underlying process. For instance, the new simulation will support scientists in comprehending the origin of the supermassive black hole at the center of the Milky Way galaxy. This includes the supermassive black hole at the center of the Messier 87 galaxy which was popularly captured by the Event Horizon Telescope in 2019.
As a next step, the scientists intend to gain an understanding of the large statistical populations of galaxies and their central black holes to better comprehend the process by which black holes form and grow under several conditions.
The study titled “Cosmological simulations of quasar fueling to sub-parsec scales using Lagrangian hyper-refinement” was financially supported by Simons Foundation, the National Science Foundation, and NASA.
Zooming into simulated galaxy
Zooming into a simulated galaxy. Video Credit: Northwestern University.
Journal Reference:
Anglés-Alcázar, D., et al. (2021) Cosmological Simulations of Quasar Fueling to Subparsec Scales Using Lagrangian Hyper-refinement. The Astrophysical Journal. doi.org/10.3847/1538-4357/ac09e8.