Northwestern astrophysicists publish report on mysterious X-shaped radio galaxies

A team of Northwestern astrophysicists, led by graduate student Aretaios Lalakos, recently released their research on X-shaped galaxies — strange phenomena that have puzzled scientists for years.

Lalakos is a member of Northwestern’s Weinberg College of Arts and Sciences and the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). He was co-advised by paper coauthor Sasha Tchekhovskoy, an assistant professor of physics and astronomy at Northwestern and key member of CIERA, and Ore Gottlieb, a CIERA postdoctoral fellow.

According to the report, the X-shape galaxies result from the interaction between the jets and the gas falling into black holes. The team’s findings were published in the Astrophysical Journal Letters on August 29.

“A popular explanation of X-shaped radio galaxies is that two galaxies collide, causing their supermassive black holes to merge, which changes the spin of the remnant black hole and the direction of the jet,” said Lalakos.

“Another idea is that the jet’s shape is altered as it interacts with large-scale gas enveloping an isolated supermassive black hole. Now, we have revealed, for the first time, that X-shaped radio galaxies can, in fact, be formed in a much simpler way.”

The formation of X-shaped galaxies has been a mystery to astronomers for nearly two decades. However, the new report provides long-awaited insight on galaxies’ creation and frequency throughout our universe.

Learn more in Northwestern Now’s article, “X-shaped radio galaxies might form more simply than expected.”