A Southwestern University astronomy professor is participating in a project that could add to our knowledge about the early history of the universe.

The project involves the study of “intergalactic medium” – clouds of gas that are located between the galaxies in the universe. Because these clouds contain primordial material from the beginning of the universe, studying them can provide important clues about the early history of the universe, including galaxy formation.

But it is not easy to study the intergalactic medium. Although the clouds may be hundreds of thousands − if not millions − of light years across, they are of such low density that they cannot be observed directly. The only way to “see” them is to study how light from more distant galaxies is absorbed as it passes through them. The absorption is revealed in the spectrum, or “light signature,” of the more distant galaxy. By studying spectra, astronomers can deduce information about the physical properties of clouds, such as density, thickness, temperature, composition and motion.

“Studying these clouds requires sophisticated computer models of how light interacts with the gas in intergalactic space,” says Mark Bottorff, an assistant professor of physics at Southwestern.

Bottorff is working on a project to develop these sophisticated computer models.

The project is funded by the Space Telescope Science Institute (STSI), which is operated for NASA and headquartered at Johns Hopkins University in Baltimore. The institute oversees all programming related to the Hubble Space Telescope.

The principal researcher on the project is Gary Ferland at the University of Kentucky, who is one of the nation’s most respected astrophysists. Bottorff did postdoctoral research with Ferland after completing his Ph.D. in physics at the University of Kentucky.

Ferland developed a computer program known as “Cloudy” that models the behavior of radiation passing through clouds of gas in space. The code for Cloudy is more than a quarter of a million lines long. Astronomers around the world use Cloudy to do their research. In addition to helping with the study of intergalactic medium, Bottorff notes that Cloudy is also used in other areas of astronomy such as the study of nebulas and quasars.

Bottorff, who has been building computer models for more than 20 years, has a $14,500 grant from STSI to create models that will help validate the Cloudy code. “This will give astronomers more confidence that the code is in working order,” he says.

Bottorff is developing four models – two for flat clouds and two for spherical clouds. He is working on models in which there is radiation hitting the clouds from just a single direction and from multiple directions (isotropic radiation). His work will model how the clouds are exposed to radiation from the Big Bang (the birth of the universe), as well as more nearby galaxies and energetic quasars. Until now, he explains, models of the clouds have been very simple because computers haven’t been fast enough to calculate more realistic models.

“With every simplification, you are less certain that the model is an accurate description of reality,” Bottorff says. “Now computers are fast enough that more sophisticated models can be built to carry out these calculations.” For example, he says, models can now be created in 2-D and 3-D instead of just 1-D.

“This is a great thing for Southwestern because it allows us to be doing astronomy on the cutting edge of astrophysics,” Bottorff says.

Kevin O’Neil, a junior majoring in physics and business, has been helping Bottorff with his research. “Kevin’s math skills are exceptional,” Bottorff says.

O’Neil, who plans to pursue graduate studies in either physics or mechanical engineering, says he has “thoroughly enjoyed” his work on the project.

“This experience highlights the benefits provided to students who attend small schools with dedicated and engaging faculty,” O’Neil says. “Dr. Bottorff has provided me with an outstanding learning opportunity.”


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