One of the longstanding mysteries of space is why galaxies start off bright and full of newborn stars and end up dark and lifeless by the end of their years. Now, a team of international researchers is suggesting that the answer lies in "red geysers," a galaxy type that can be used as a model for understanding this process.
Red geysers possess intense stellar winds that the team believes are caused by supermassive black holes with a lower-than-average level of energy. Furthermore, the data suggests that these winds increase the amount of the galaxies' gases and prevent the cooling and condensation that stimulates star formation.
"Stars form from the gas, a bit like the drops of rain condense from the water vapor," said Michele Cappellari, an astrophysicist at Oxford University and co-author of the study. "And in both cases one needs the gas to cool down, for condensation to occur. 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," she added.
Cappellari and her team used data from the MaNGa galaxy survey to examine the red geyser candidates in 3D and create models that portray the movement of gas inside of them and the course of their stellar winds.
"The discovery was made possible by the amazing power of the ongoing MaNGA galaxy survey," said Kevin Bundy from the University of Tokyo, who led the collaboration. "The survey allows us to observe galaxies in three dimensions, by mapping not only how they appear on the sky, but also how their stars and gas move inside them."
Examination of the mechanical action of the stellar winds explains how ambient gas is heated and prevented from undergoing condensation in dormant galaxies.
"Stars form from the gas, but in many galaxies stars were found not to form despite an abundance of gas," said Edmond Cheung, a researcher at the University of Tokyo and lead author of the study. "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," he concluded.
The findings were published in the May 25 issue of the journal Nature.
