Newly-discovered "red geyser" galaxies may be responsible for galactic warming

Artist's impression of Akira drawing matter away from Tetsuo(Credit: Kavli IPMU)

An international team of scientists may have discovered the key to a phenomena known as "galactic warming," which is thought to be responsible for a dramatic drop-off in star production on galactic scales. Prior to the study, the cause of the warming was largely unknown, though it had been linked to the presence of the supermassive black holes lurking at the center of dormant galaxies.

Ordinarily, stars form out of interstellar clouds of dust and gas, which cool over time, allowing knots to form. If these knots, or clumps, accrue enough mass, they collapse in on themselves, forming the core of a newly-born star. Galactic warming is thought to prevent this from taking place by constantly heating the gas, leaving the star-forming material too hot and energetic to settle and form the initial clumps.

Previous studies hinted at black holes as the cause of the phenomenon, though up until now no direct observations had been made to confirm the theory. This is due to the inherent difficulties in mapping the structure of materials on a galaxy-wide scale, and the speed at which black hole events can occur.

The missing evidence was discovered by astronomers taking part in the new component survey of the Sloan Digital Sky Survey known as "Mapping Nearby Galaxies at Apache Point Observatory" (MaNGA). The team spotted a galaxy with all of the correct ingredients to generate a new generation of stars, yet which was populated solely by older stellar bodies due to galactic warming. This newly-discovered form of galaxy is known as a red geyser, so named due to the reddish tinge of the aged stars.

"MaNGA is an ambitious survey, aiming to observe 10,000 galaxies in total," states Dr. Anne-Marie Weijmans of the University of St. Andrews' School of Physics and Astronomy, one of the scientists responsible for the discovery. "But because we observe such a large number of galaxies, we are able to catch the rare ones and discover new cases, such as these red geysers."

The first of these newly-discovered red geyser galaxies has been given the nickname Akira, while a nearby companion galaxy has been tentatively named Tetsuo. The astronomers found that the supermassive black hole at the center of Akira was siphoning away and consuming vast amounts of material from Tetsuo, and using it to fuel powerful solar winds.

Astronomers believe that the winds emitted by the black hole are energizing and heating the gas in Akira to temperatures above the star formation threshold. Alarmingly, the team behind the research have suggested that the Milky Way is not immune to this effect, and that our galaxy may one day become a red geyser, transformed by the winds generated by our central supermassive block hole Sagittarius A*.

A paper on the research has been published online in the journal Nature.

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