An international team of astronomers has detected a signal from dying galaxies’ active supermassive black holes in the early Universe.
According to the researchers in the paper published in the Astrophysical Journal, the appearance of these active supermassive black holes correlates with changes in the host galaxy, implying that a black hole could have far-reaching effects on the evolution of its host galaxy.
The Milky Way Galaxy, in which we live, contains stars of various ages, including stars that are still forming. However, in some galaxies, known as elliptical galaxies, all of the stars are old and roughly the same age. This suggests that elliptical galaxies experienced a period of prolific star formation early in their histories, which abruptly ended.
It is unclear why star formation stopped in some galaxies but not others. One theory is that a supermassive black hole disrupts the gas in some galaxies, creating an unsuitable environment for star formation.
Astronomers from Japan, Mexico, Denmark, France, Italy, and the United States examined distant galaxies 9.5-12.5 billion lightyears away to put this theory to the test.
They used a database that combined observations from the world’s best telescopes, such as Japan’s 8.2-metre Subaru Telescope and the Atacama Large Millimetre/submillimetre Array (ALMA).
The team first used optical and infrared data to separate galaxies into two groups: those that are still forming stars and those that have stopped. The signal-to-noise ratio of the x-ray and radio wave data was insufficient to distinguish individual galaxies.
As a result, the team combined data from different galaxies to create images with a higher signal-to-noise ratio of “average” galaxies. The team confirmed x-ray and radio emissions for galaxies without star formation in the averaged images. This is the first time such emissions from distant galaxies more than 10 billion lightyears away have been detected.
Furthermore, the findings show that the x-ray and radio emissions are too powerful to be explained by the galaxy’s stars alone, indicating the presence of an active supermassive black hole. This black hole activity signal is weaker in galaxies that are undergoing star formation.
The findings show that a sudden cessation of star formation in the early Universe correlates with increased supermassive black hole activity.
