She loves a 'starry night:' Cosmology student searches universe for neutralinos

Argyro “Iro” Tasitsiomi

Turbulent swirls of ambiguously colored paint flow across the canvas of Vincent van Gogh’s “Starry Night.” Eleven stars and the moon glow concentrically against a dark sky. A French village nestles against rolling hills on the horizon.

Art connoisseurs have admired the masterpiece for more than a century now.

“I’d just love to have been the painter of ‘Starry Night,’ ” said Argyro “Iro” Tasitsiomi, a graduate student in Astronomy & Astrophysics. Tasitsiomi produces abstract oil paintings alongside research papers on the detection of dark matter, a mysterious cosmic substance that is no less ineffable than the psyche of van Gogh himself. One of her most recent scientific works on dark matter appeared in the August issue of the International Journal of Modern Physics D.

Tasitsiomi has kept her scientific side separate from her art, but she theorizes that both interests spring from the need to understand, whether it is the workings of her own mind or the origin of the universe. Think of it as a matter of pattern recognition. Look, she said, at how cosmologists have pieced together the early evolution of the universe from the faint afterglow of the big bang, known scientifically as the cosmic microwave background.

“It could be just a mess of hot and cold spots, but people came up with good ways to physically extract information out of it,” Tasitsiomi said.

Her journal article was itself an impressive act of information extraction, said Sean Carroll, Assistant Professor in Physics and the College. Tasitsiomi wrote the core of her paper as an assignment for Carroll’s cosmology class.

“The paper Iro handed in was much more thorough and comprehensive than anything you would expect in a typical final paper,” Carroll said. He encouraged her to expand it into a publishable scientific review, a summary of the state of knowledge on a given subject that graduate students rarely undertake.

“The paper has now become a useful reference to the scientific community. Iro has fantastic talent and ambition, and she should go far,” Carroll said.

Tasitsiomi chose as her topic the puzzling behavior of dark matter, sort of a puzzle within a puzzle. The puzzle: dark matter accounts for more than 90 percent of all matter in the universe, but no one knows what it is. Although invisible to telescopes, scientists can observe the gravitational influence it exerts over galaxies.

The puzzle within a puzzle: simulations of dark matter behavior suggest that it should become very dense at the center of galaxies. Observations have failed to confirm this behavior.

Today, Tasitsiomi and her adviser, Angela Olinto, Chair and Associate Professor of Astronomy & Astrophysics, are conducting theoretical studies aimed at narrowing the search for viable dark matter candidates. Particle physicists have proposed a theoretical subatomic particle called the neutralino as the most plausible candidate, but its exact properties remain uncertain.

Tasitsiomi and Olinto are using the neutralino’s predicted properties and the sensitivities of a variety of instruments, which are already are in operation or soon will be in operation, to find ways to detect the neutralino. “We are taking a rough look at how dark the dark matter would be and why we aren’t seeing it yet,” Olinto said.

The neutralino has two factors going for it, Tasitsiomi said.

“First of all, it does not decay, because if it decayed it wouldn’t be out there in significant amounts to account for the dark matter,” she said. “The other good thing is that the neutralino is an annihilating particle.” And when neutralinos annihilate, they produce quark jets. The quark jets lead to the formation of both neutral and charged particles that, in the decay process, emit gamma rays and synchrotron radiation in the presence of magnetic fields, respectively.

It is possible, according to Tasitsiomi, Olinto and Jennifer Gaskins, a Chicago graduate student in Physics, that the Gamma Ray Large Area Space Telescope will be able to detect those gamma rays after it is launched in 2006.

“Even the non-detection will be able to give you some important information about neutralino parameters,” Tasitsiomi said. “You will be able to shrink their parameter space, at least. That’s a very important thing given how wide they are.”

Meanwhile, the range of possibilities remains perhaps as wide as the interpretations she hears about one of her paintings.

“Every time I have a guest, he or she has to go through the testing procedure of what they understand about it,” Tasitsiomi said. “I’ve heard so many interpretations, which is such a wonderful thing.”