Astronomers have uncovered a new type of galaxies, dubbed ‘red geysers,’ with supermassive black hole winds so intense and hot that stars can’t form.
An artist’s rendition of the Akira (right) and Tetsuo (left) galaxies in action. Akira’s gravity pulls Tetsuo’s gas into its central supermassive black hole, fueling winds that have the power to heat Akira’s gas. Because of the action of the black hole winds, Tetsuo’s donated gas is rendered inert, preventing a new cycle of star formation in the Akira galaxy. Image credit: Kavli IPMU.
Devoid of fresh young stars, old red galaxies make up a large fraction of galaxies in the Local Universe, but a mystery that has plagued scientists for decades has been how these objects remain inactive despite having all of the ingredients needed to form stars.
Now, thanks to the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory (SDSS-IV MaNGA) survey, a team of astronomers has discovered a supermassive black hole in the act of heating gas within its host galaxy, leading to the prevention of star formation.
“Stars form from the gas, but in many galaxies stars were found not to form despite an abundance of gas,” said lead author Dr. Edmond Cheung, from the University of Tokyo.
“It was like having deserts in densely clouded regions,” he added.
“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.”
Dr. Cheung and co-authors studied a galaxy nicknamed Akira, a prototypical example of the ‘red geyser’ galaxy (‘red’ referring to the color of galaxies that lack young blue stars, and ‘geyser’ referring to the episodic wind outbursts from the supermassive black hole).
This galaxy showed intriguing and complex patterns of warm gas, implying the presence of an outflowing wind from the galaxy’s central supermassive black hole.
“The fuel for Akira’s supermassive black hole likely came from the interaction with a smaller galaxy, nicknamed Tetsuo,” Dr. Cheung and his colleagues said.
“The outflowing wind had enough energy to heat the surrounding gas through shocks and turbulence and could ultimately prevent any future star formation.”
The researchers describe their findings in the May 26, 2016 issue of the journal Nature.
They will continue to analyze the SDSS-IV MaNGA data and plan a number of follow-up studies to further reveal the role of red geysers on the evolution of galaxies.
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Edmond Cheung et al. 2016. Suppressing star formation in quiescent galaxies with supermassive black hole winds. Nature 533, 504-508; doi: 10.1038/nature18006
