How Galaxies Feed their Supermassive Black Holes

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  • Galaxies’ spiral arms ‘put the brakes on gas,’ enabling it to fall into the black hole
  • As gas heats up while falling into a black hole, it turns into a bright quasar
  • Simulation models gas flow with 1,000 times better resolution than previously possible, while comprehensively incorporating numerous forces and factors at play
Started at Northwestern University, the simulation is the first to show, in great detail, how gas flux in the universe all the way down to the center of a supermassive black hole. While other simulations have modeled black hole growth, this is the first single computer simulation powerful enough to comprehensively account for the numerous forces and factors that play into the evolution of supermassive black holes. This simulations show the growth at 1000 times the previous simulatoins.


“Other models can tell you a lot 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,” said lead author Daniel Anglés-Alcázar.

“It turns out, it is very important to connect all these processes at the same time,” he said.

The simulation also gives rare insight into the mysterious nature of incredibly luminous quasars fast-growing black holes. Some of the brightest objects in the universe, quasars often even outshine entire galaxies.

“The light we observe from distant quasars is powered as gas falls into supermassive black holes and gets heated up in the process,” said Northwestern’s Claude-André Faucher-Giguère, one of the study’s senior authors. “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.”

The research was published Aug. 17 in the Astrophysical Journal .

Equivalent to the mass of millions or billions of suns, supermassive black holes can swallow nearly 10 times the mass of a sun in just one year. But while some supermassive black holes enjoy a continuous supply of food, others go dormant for millions of years, only to reawaken abruptly with a serendipitous influx of gas. The details about how gas flows across the universe to feed supermassive black holes have remained a long-standing question.

The new tool from researchers at Northwestern University accounts for the many factors that affect the growth of black holes. It details how gas flows across the universe, before being pulled up by a galaxy’s spiral arms, made of young stars, to sustain the ginormous black hole at its center.

To address this mystery, the research team developed the new simulation, which incorporates many of the key processes, including the expansion of the universe and the galactic environment on large scales, gravity gas hydrodynamics and feedback from massive stars, into one model.

With the new simulations, researchers can finally model how this happens. For example, the new simulation will help researchers understand the origin of the supermassive black hole at the center of our own Milky Way galaxy as well as the supermassive black hole at the center of the Messier 87 galaxy, which was famously captured by the Event Horizon Telescope in 2019. Next, the researchers aim to study large statistical populations of galaxies and their central black holes to better understand how black holes can form and grow under various conditions.






Reference:
Link to: Northwestern Now Story

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