Dying Early Universe Galaxies Could Be Killed by Their Supermassive Black Holes

The Milky Way is not very active. Every year, it produces around three to four Suns worth of new stars in the entire spiral body, and stars of all ages can be found sprinkled throughout.

Most star formation ceased long ago in elliptical galaxies, which are even quieter. Most stars in the galaxies can't be found younger than a certain age, suggesting that star formation stopped abruptly.

It's not clear how star formation is switched off in these smooth, nearly featureless galaxies, but it's believed to be related to the supermassive black holes found at the center of every galaxy. Kei Ito of the Graduate University for Advanced Studies in Japan is leading a team of scientists who peered back into the early Universe to find out if that is the case.

Using some of the world's most powerful telescopes, they have collected data in multiple wavelength of light to identify ancient galaxies that have traveled over a billion years across the gulf of space-time.

The first thing to do was to use optical and IR data to find out which star formation is continuing and which has stopped.

X-ray and radio data were used to identify black hole activity. Astronomers believe that star formation may be quenched by this mechanism. When a black hole is active, it takes a lot of matter from the space around it. This process is violent and messy and produces feedback.

The space around a black hole is different from what we know about the horizon of a black hole. The material swirls around the black hole, like water around a drain, and the gravity causes intense radiation that blazes across the Universe.

jets blasting from the black hole's polar regions are a form of feedback. Material outside the event horizon is thought to be accelerated along the black hole's exterior magnetic field, to be launched from the poles as powerful, focused jets of plasma that travel at a significant percentage of the speed of light.

The winds that sweep out into their galaxies are generated by active supermassive black holes. The three forms of feedback, the radiation, the jets and the winds, are thought to push away the cold molecular gas that is required for the formation of baby stars.

Our view of the here and now is very different from our view across such a large expanse of space. The researchers had to stack the galaxies together in order to emphasize the radio and X-ray light that is telltale of an active black hole.

The team found an excess X-ray and radio signal that was too strong to be explained by the stars alone. An active black hole is the best explanation for this signal. The signal was not as pronounced in the galaxies with ongoing star formation.

The researchers concluded that an active black hole could be to blame for the sudden deaths of these mysterious, ghostly galaxies.

Future research may shed light on the physics of this mysterious process.

The research has been published.

The Hubble Heritage Team/STScI/AURA is credited with the cover image.