A red geyser, pictured right, is seen pulling gas from a neighboring galaxy, creating stellar winds that heat its ambient gas and prevent the cooling and condensation necessary for star formation. Photo by Kavli IPMU
OXFORD, England, May 25 (UPI) -- Astronomers continue to struggle with an explanation for dark and dimming galaxies. Why do galaxies start out bright, colorful and rich with newborn stars, yet end up dark and lifeless as they age?
New research may offer an answer. Astronomers are looking to a recently discovered galaxy type called "red geysers" as a model for understanding what keep galaxies "turned off."
Red geysers feature intense stellar winds, which scientists believe are powered by low-energy supermassive black holes. These winds heat up the galaxies' abundance of gas and inhibits the cooling and condensation necessary for the formation of new stars.
"Stars form from the gas, a bit like the drops of rain condense from the water vapor. And in both cases one needs the gas to cool down, for condensation to occur," Michele Cappellari, an astrophysicist at Oxford University, said in a news release. "But we could not understand what was preventing this cooling from happening in many galaxies. But when we modeled the motion of the gas in the red geysers, we found that the gas was being pushed away from the galaxy center, and escaping the galaxy gravitational pull."
Cappellari is the co-author of a new paper on the discovery and analysis of red geyser galaxies, published this week in the journal Nature.
Researchers were able to study the red geyser candidates in 3D using data collected by the MaNGA galaxy survey. The data allowed them to model the movement of gas inside the galaxies and plot the course of stellar winds.
The mechanical action of the stellar winds explains how ambient gas is heated and kept from condensing in dormant galaxies.
"Stars form from the gas, but in many galaxies stars were found not to form despite an abundance of gas," explained lead study author Edmond Cheung, a researcher at the University of Tokyo's Kavli Institute for the Physics and Mathematics of the Universe. "It was like having deserts in densely clouded regions."
"We knew quiescent galaxies needed some way to suppress star formation, and now we think the red geysers phenomenon may represent how typical quiescent galaxies maintain their quiescence," Cheung concluded.