Cracking a mystery of massive black holes and quasars with supercomputer simulations
Researchers address some of the questions surrounding these massive and enigmatic features of the universe by using new, high-powered simulations.
You've heard of black holes. The supermassive space bodies devouring everything that crosses their path. But have you ever thought about how they are actually fed, how gas flows across the universe just to become fuel for them?
UConn Assistant Professor of Physics Daniel Anglés-Alcázar, lead author on a paper in The Astrophysical Journal, addresses some of the questions surrounding these massive and enigmatic features of the universe by using new, high-powered simulations.
"Supermassive black holes play a key role in galaxy evolution and we are trying to understand how they grow at the centers of galaxies," says Anglés-Alcázar. "This is very important not just because black holes are very interesting objects on their own, as sources of gravitational waves and all sorts of interesting stuff, but also because we need to understand what the central black holes are doing if we want to understand how galaxies evolve."
Galaxy formation, as Anglés-Alcázar states, starts with a halo of dark matter that dominates the mass and gravitational potential in the area and begins pulling in gas from its surroundings. Stars form from the dense gas, but some of it must reach the center of the galaxy to feed the black hole. How does all that gas get there? For some black holes, this involves huge quantities of gas, the equivalent of ten times the mass of the sun or more swallowed in just one year, says Anglés-Alcázar.
"When supermassive black holes are growing very fast, we refer to them as quasars," he says. "They can have a mass well into one billion times the mass of the sun and can outshine everything else in the galaxy. How quasars look depends on how much gas they add per unit of time. How do we manage to get so much gas down to the center of the galaxy and close enough that the black hole can grab it and grow from there?"
"Our simulations incorporate many of the key physical processes, for example, the hydrodynamics of gas and how it evolves under the influence of pressure forces, gravity, and feedback from massive stars. 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."
With hundreds of CPUs running in parallel, Anglés-Alcázar says, they could have easily taken the length of millions of CPU hours.
"This is the first time that we have been able to create a simulation that can capture the full range of scales in a single model and where we can watch how gas is flowing from very large scales all the way down to the very center of the massive galaxy that we are focusing on."
This is just the beginning of our next level of understanding the universe and our own galaxy. With the continuous development of our computing technology and software, I am sure, we are going to unveil the greatest mysteries of this world.
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