Astronomers publish map with 25,000 supermassive black holes

An international team of astronomers has published a map of the sky showing more than 25,000 supermassive black holes. The card is published in the magazine Astronomy & Astrophysics, is the most detailed sky map in the field of so-called low radio frequencies. The astronomers, including Leiden astronomers, used 52 stations with LOFAR antennas spread across nine European countries.

Stars or black holes?

To an untrained eye, it appears that the aerial map contains thousands of stars, but these are actually supermassive black holes. Each black hole is located in a different, distant galaxy. The radio emission is emitted by matter emitted as it approaches the black hole.

The research leader, Francesco de Gasperin (formerly University of Leiden, now Universität Hamburg, Germany), says of the study: “It is the result of many years of work on incredibly difficult data. We had to invent new methods to convert the radio signals. in images of the sky. “

From the bottom of the pool

Observations at long radio waves are complicated by the ionosphere that surrounds the Earth. This layer of free electrons acts like a cloudy lens that is constantly moving across the radio telescope. Co-author Reinout van Weeren (Sterrewag Leiden) explains: “It’s similar to trying to see the world while immersed in a pool. When you look up, the waves on the pool water divert the light rays and distort them. the considered. “

Map of the whole sky

The new map was created by combining 256 hours of observations of the northern sky. The researchers used supercomputers with new algorithms that correct the effect of the ionosphere every four seconds. Huub Röttgering, scientific director of the Leiden Observatory, is the last author of the publication. He is delighted with the results: “After many years of software development, it’s so amazing to see that it’s really worked out now.”

The map now covers 4 percent of the northern half of the sky. The astronomers plan to continue until they have mapped the entire northern sky. In addition to supermassive black holes, the map also provides insight into the large-scale structure of the universe.