Long-lived radio outburst from black hole exhibits properties of the early universe

Short-lived sources of radio radiation in the sky, known as radio transients, can originate in the vicinity of supermassive black holes in the centers of galaxies. They are the result of processes that take place under extreme physical conditions. While most radio transients associated with galactic centers last only days or weeks, the galaxy SDSS J110546.07+145202.4 has been shining very brightly in radio light for several years—the first source of its kind.

An international team led by Stefanie Komossa from the Max Planck Institute for Radio Astronomy (MPIfR) studied this unique galaxy using new observations and archival data ranging from low-energy radio waves to high-energy X-rays. The results were published in The Astrophysical Journal.

Loud and long-lasting

The spiral galaxy SDSS J110546.07+145202.4 is located about 1.8 billion light-years from Earth in the constellation Leo. The intensity of its radio emission increased more than 20-fold in a short period and shows no signs of weakening. For more than eight years, the galaxy has been shining exceptionally brightly in the radio regime—about 10 quadrillion (10¹⁶) times as intensely as our sun.

“We are dealing with the prototype of a new class of galaxies that undergo rapid changes in radio emission,” comments co-author Phil Edwards from CSIRO, Australia’s national science agency.

The source of the radiation is located near the black hole at the galaxy’s center. This black hole has a comparatively low mass, which is increasing exceptionally fast, however, through the accretion of matter.

“Luminous radio radiation from rapidly growing, lightweight black holes is rare to begin with. Their transition into a long-lasting, radio-bright state has never been observed before,” reports lead author Stefanie Komossa.

“Follow-up observations with numerous telescopes, including the 100-meter (328-foot) radio telescope in Effelsberg, CSIRO’s Australia Telescope Compact Array, and satellites in space, confirm the source’s unique properties,” adds co-author Alexander Kraus.

Based on the extensive data set, the team suspects that more matter has been falling into the black hole for several years, which in turn has triggered a jet—a concentrated beam of particles traveling at nearly the speed of light that emits radiation. Why exactly more matter is falling into the black hole and why the outburst has lasted so long has not yet been conclusively determined.

A local laboratory for the early universe

A low mass and rapid growth are precisely the properties of central black holes that one would expect from galaxies in the early universe. Compared with these distant sources, however, SDSS J110546.07+145202.4 is located in our cosmic neighborhood. This allows for detailed observations and insights into the physical processes surrounding the evolution of black holes and the formation of jets.

“Such high-energy events can provide astronomers with a wealth of insights. By observing these jets and outbursts, we can study the physical processes in some of the most extreme environments in the universe,” says co-author Kovi Rose from the University of Sydney’s Sydney Institute for Astronomy.

In the future, high-resolution instruments such as the Very Long Baseline Array (VLBA) will make it possible to map the structure of the jet and track the evolution of the radio emission over the coming years.

“With sensitive facilities like the incoming SKA telescopes, we’ll be able to identify similar radio transients in future sky surveys. This is crucial for filling the gaps in our understanding of the early universe,” explains Komossa.

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