Astrophysics Simulations

 

Researchers in the group of Professor Tom Jones (MSI Fellow; Astronomy) are engaged in a long-term, unique, and highly successful study of the dynamics of diffuse, conducting media in astrophysical environments and their roles in mediating the acceleration and propagation of high-energy charged particles (so-called “cosmic rays”). The group has developed codes that combine high-performance, highly scalable, multidimensional magnetohydrodyamics (MHD) algorithms with uniquely efficient treatments of diffusive transport of cosmic rays.

 

In the image above, the left side illustrates results from an innovative MHD simulation carried out in November by Pete Mendygral and Tom Jones on MSI's Itasca supercomputer. The right side shows radio (pink) and X-ray (blue) astronomical observations of the astrophysical system that the simulation was intended to model (image credit: NASA and the National Radio Astronomy Observatory). The simulation modeled the dynamics of two pairs of supersonic, magnetized plasma jets. The jets were generated from sources that were orbiting each other while being subjected to a strong, supersonic cross wind. This simulation, which took roughly 10,000 CPU hours to complete, is the first of its kind. It was possible to set up, test, and execute the simulation over a span of three days prior to a symposium because of excellent HPC support from MSI. The underlying science is described below.

The jets represent highly supersonic outflows from massive black holes at the centers of a pair of merging galaxies that are components of a pair of merging clusters of galaxies. As the black holes swallow nearby matter some of the energy released drives fast jets along the spin axes of the black holes. These are details of ongoing construction in the universe. On the biggest scales, clusters of galaxies spanning millions of light years fall together due to mutual gravity and collide to form bigger clusters over a time span of a few billion years. Some of the individual galaxies within those clusters also fall together, collide and merge together over time spans of a few hundred million years. Astronomers have established that all galaxies have massive black holes anchoring their centers.  As two galaxies merge, gravitational effects cause their individual black holes to merge as well, also over a span of about 100 million years. Although cluster mergers are long lived enough to make them easy to find, it is much rarer to witness the faster merger of two massive black holes. But there are examples, including the very interesting pair of black holes in the galaxy cluster known as Abell 400, which is about 300 million light years from Earth. In this case two galaxies and their black holes are bound into an orbit about 20,000 light years apart and just beginning their inward spiral towards a merger. Each black hole, as it turns out is making plasma jets, so both are easy to find. The orbital motions of the black holes is causing the jets to become intertwined. At this point in the cluster merger the hot atmosphere of the clusters (revealed by X-rays) is "sloshing" in the gravitational well of the combined system. In effect the two merging galaxies are sitting in a very strong wind, which is blowing away the radio jets.

 

Work by Dr. Mendygral that involved a large data transfer was featured in a previous Research Spotlight.
 

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