The University of Tokyo and the University of Oxford have uncovered a new phenomenon within galaxies that they have named red geysers, which may be able to explain exactly how and why the process takes place. Red geysers house supermassive black holes with low amounts of energy that cause fierce interstellar winds. The winds are so strong that they actually suppress star formation due to their intense heat, preventing ambient gas from cooling and compressing into stars.
Galaxies start their lives as colorful and cheerful, loaded with gas and dust and forming new stars on a regular basis. As galaxies age, they begin to slowly produce fewer numbers of stars and turn into “graveyards” or “deserts” in the sky and stay that way throughout the rest of their evolution. What causes galaxies to drastically change so much over their lifespan has remained a mystery of galaxy evolution for quite some time.
Dr. Edmond Cheung, lead author of the study says stars form from the gas, but in many galaxies stars were not forming even when large amounts of gas were present. The team already knew quiescent galaxies needed a way to suppress the formation of stars but now they believe that red geysers may display just how typical quiescent galaxies keep their quiescence.
Co-author Dr. Michele Cappellari explains that stars form from gas, requiring one gas in the equation to cool for condensation to occur (just like how drops of rain condense from water vapor). Previously, she and the rest of the team were not able to understand what was halting this natural cooling process from occurring in many galaxies. When researchers modeled the motion of the gas within the red geysers, it was discovered that the gas was being directed away from the center of the galaxy, exiting the galaxy’s gravitational pull.
The observation was found thanks to the MaNGA galaxy survey which allowed researchers to view galaxies in three dimensions. They were able to map how galaxies appear in the sky and also how their stars and gases move throughout them. A just-about dormant galaxy named Akira was used as their prototypical example, which the researchers used to view how the wind’s driving mechanism was likely to originate within the galactic nucleus of Akira. The energy created by the nucleus was powered by a supermassive black hole, producing wind. That wind provides enough mechanical energy to heat ambient, cooler gas within the galaxy, suppressing the formation of stars.
The name red geysers came from the episodic quality present within the strong winds; and “red” was used because of the lack of blue amongst young stars. This new phenomenon appears to be very common and could be used to better understand and study all quiescent galaxies.
The research,”Suppressing star formation in quiescent galaxies with supermassive black hole winds“, was published in Nature journal.