Black holes love to eat, but they have different table manners

All supermassive black holes in the centers of galaxies appear to have periods when they swallow matter from their close environment. But that’s about what the similarities are about. That is the conclusion of British and Dutch astronomers from their research with ultra-sensitive radio telescopes in a well-studied part of the universe. They publish their findings in two articles in the international journal Astronomy and Astrophysics

Astronomers have been studying active galaxies since the 1950s. Active galaxies have a supermassive black hole at their center that gobbles up matter. During these active phases, the objects often emit extremely strong radio, infrared, ultraviolet and X-rays.

In two new publications, an international team of astronomers focused on all active galaxies in the well-studied GOODS North region in the Ursa Major constellation. Until now, that area has mainly been studied by space telescopes that collect visible light, infrared light and UV light. The new observations add data from sensitive radio telescope networks, including the UK national facility e-MERLIN and the European VLBI Network (EVN).

Thanks to this systematic study, three things became clear. First, it turns out that the nuclei of many different types of galaxies can be active in different ways. Some are extremely greedy and gobble up as much material as possible; others digest their food more slowly, and others are nearly hungry.

Second, an accretion phase occasionally occurs simultaneously with a star formation phase and sometimes does not. When star formation is underway, activity in the nucleus is difficult to detect.

Third, the nuclear accretion process may or may not generate radiojets – regardless of the speed at which the black hole swallows its food.

According to lead researcher Jack Radcliffe (formerly University of Groningen and ASTRON in the Netherlands and University of Manchester in the United Kingdom, now University of Pretoria, South Africa), the observations also show that radio telescopes are optimally useful for examining the eating habits of black holes in the distant universe. . “That’s good news, because the SKA radio telescopes are coming and they will allow us to look deeper into the Universe with even more detail.”

Co-author Peter Barthel (University of Groningen, The Netherlands) adds: “We are getting more and more indications that all galaxies have massive black holes in their centers. These must of course have grown to their current mass. Thanks to our observations, we now have these growth processes. in sight and slowly but surely we begin to understand them. ”

Co-author Michael Garrett (University of Manchester, UK) added: “These wonderful results demonstrate the unique capabilities of radio astronomy. Telescopes such as the VLA, e-MERLIN and the EVN are transforming our view of how galaxies evolve in the early years. universe. ”