NASA scientists create jets of black holes with a supercomputer

Using NASA’s Climate Simulation Center (NCCS), scientists at NASA’s Goddard Space Flight Center ran 100 simulations exploring jets – narrow beams of energetic particles – that emerge at speeds near light from supermassive black holes. These behemoths sit at the center of active star-forming galaxies like our own galaxy, the Milky Way, and can weigh millions to billions of times the mass of the sun.

As jets and winds escape from these active galactic nuclei (AGNs), they “regulate the gas at the center of the galaxy and affect things like the rate of star formation and how the gas mixes with the surrounding galactic environment,” the study leader explained. Ryan Tanner, post-doctoral fellow at NASA Goddard’s X-ray Astrophysics Laboratory.

“For our simulations, we focused on the less studied, low-luminosity jets and how they determine the evolution of their host galaxies.” said Taner. He collaborated with X-ray Astrophysics Laboratory astrophysicist Kimberly Weaver on the computational study, which appears in The Astronomical Journal.

Observational evidence of jets and other AGN fluxes came first from radio telescopes and later from NASA and European Space Agency X-ray telescopes. Over the past 30 to 40 years, astronomers including Weaver have pieced together an explanation for their origin by linking optical, radio, ultraviolet, and X-ray observations (see next image below).

“High-luminosity jets are easier to find because they create massive structures that can be seen in radio observations,” Tanner explained. “Dim jets are difficult to study by observation, so the astronomical community doesn’t understand them as well.”

Enter simulations compatible with NASA supercomputers. For realistic starting conditions, Tanner and Weaver used the total mass of a hypothetical galaxy the size of the Milky Way. For gas distribution and other AGN properties, they looked to spiral galaxies such as NGC 1386, NGC 3079, and NGC 4945.

Tanner modified the Athena astrophysical hydrodynamics code to explore the impacts of jets and gas on each other across 26,000 light-years of space, or about half the radius of the Milky Way. From the full set of 100 simulations, the team selected 19, which consumed 800,000 core hours on the NCCS Discover supercomputer, for publication.

“Being able to use NASA’s supercomputing resources allowed us to explore a much larger parameter space than if we had to use more modest resources,” Tanner said. “It led to uncovering important relationships that we couldn’t uncover with a more limited scope.”

The simulations revealed two major properties of low-light jets:

• They interact with their host galaxy much more than high-luminosity jets.
• They affect and are affected by the interstellar medium in the galaxy, leading to a greater variety of shapes than high-luminosity jets.

“We have demonstrated the method by which AGN impacts its galaxy and creates the physical features, such as shocks in the interstellar medium, that we have observed for about 30 years,” Weaver said. “These results compare well to optical and X-ray observations. I was surprised at how well the theory matches the observations and answers long-standing questions I have about AGN that I studied in as a graduate student, such as NGC 1386! samples.”