First, radio telescopes and then X-ray telescopes operated by NASA and the European Space Agency provided observational evidence for jets and other AGN outflows. Astronomers, including Weaver, have cobbled an explanation for their genesis during the past 30 to 40 years by tying together optical, radio, ultraviolet, and X-ray evidence.
Due to the huge structures they produce, high-luminosity jets are easier to locate in radio measurements. Since low-luminosity jets are difficult to observe, the astronomy community must fully comprehend them.
Using the NASA Center for Climate Simulation (NCCS), scientists from NASA Goddard Space Flight Center ran 100 simulations exploring jets that emerge at nearly light speed from supermassive black holes.
Study lead Ryan Tanner, a postdoc in NASA Goddard’s X-ray Astrophysics Laboratory, said, “As jets and winds flow out from these active galactic nuclei (AGN), they regulate the gas in the center of the galaxy and affect things like the star-formation rate and how the gas mixes with the surrounding galactic environment.”
“Our simulations focused on less-studied, low-luminosity jets and how they determine the evolution of their host galaxies.”
Enter NASA supercomputer-enabled simulations. Scientists employed the total mass of a hypothetical galaxy around the size of the Milky Way to create realistic starting conditions. They studied spiral galaxies like NGC 1386, NGC 3079, and NGC 4945 to determine the gas distribution and other AGN features.
Later, scientists modified astrophysical hydrodynamics code to explore the impacts of the jets and gas on each other across 26,000 light-years of space, 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.
Tanner said, “Using NASA supercomputing resources allowed us to explore a much larger parameter space than if we had to use more modest resources. This led to uncovering important relationships we could not discover with a more limited scope.”
The simulations uncovered two significant properties of low-luminosity jets:
- They interact with their host galaxy much more than high-luminosity jets.
- They both affect and are affected by the interstellar medium within the galaxy, leading to a greater variety of shapes than high-luminosity jets.
X-ray Astrophysics Laboratory astrophysicist Kimberly Weaver said, “We have demonstrated the method by which the AGN impacts its galaxy and creates the physical features, such as shocks in the interstellar medium, that we have observed for about 30 years. These results compare well with optical and X-ray observations. I was surprised at how well the theory matches observations and addresses longstanding questions about AGN that I studied as a graduate student, like NGC 1386! And now we can expand to larger samples.”