(ORDO NEWS) — Scientists from Northwestern University have conducted a new study that sheds light on the formation of X-shaped galaxies. The article was published August 29 in The Astrophysical Journal Letters.
Using modeling, astrophysicists have created conditions under which a black hole, actively “feeding”, forms jets and an accretion disk. The fulfillment of these conditions unexpectedly led to the formation of an X-shaped radio galaxy.
The researchers found that the galaxy’s characteristic X-shape is the result of an interaction between jets and gas falling into the black hole.
During the simulation, the gas deflected the newly formed jets, which “turned on” and “off”, oscillated randomly and inflated pairs of cavities in different directions, creating an X-shape.
However, eventually the jets became strong enough to push through the gas. At this moment, the jets stabilized, stopped swinging, and spread along one axis.
“We have shown for the first time that X-shaped radio galaxies can be formed in a much simpler way,” said Aretaios Lalakos, a graduate student at the Weinberg Northwestern College of Arts and Sciences and a member of the Center for Interdisciplinary Research and Research in Astrophysics (CIERA).
He is co-authored by Sasha Chekhovsky, associate professor of physics and astronomy at Northwestern University and member of CIERA, and Ore Gottlieb, CIERA postdoc.
First discovered in 1992, X-shaped radio galaxies make up less than 10% of all radio galaxies. Since the X-shaped form appeared only at the beginning of the simulation – until the jets strengthened and stabilized – Lalakos decided that X-shaped radio galaxies can appear in the Universe more often, but live much less than previously thought.
“It’s impossible to walk right up to the center and see what’s happening next to a black hole,” Lalakos said.
“If a supermassive black hole has already formed, we can’t observe its evolution because human life is too short. In most cases, we can only rely on simulations to understand what’s going on around a black hole.”
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