An international team of researchers from the Max Planck Institute for Radio Astronomy (MPIfR) has recently made a groundbreaking discovery while observing SDSS J110546.07+145202.4, a spiral galaxy situated roughly 1.8 billion light-years from Earth in the constellation Leo. Over a span of eight years, this galaxy shone exceptionally brightly in the radio spectrum, driven by intense radiation emanating from a supermassive black hole (SMBH) at its core.
It is known that transient radio sources occasionally emerge near black holes due to the extreme physical conditions within their accretion disks. This phenomenon, referred to as an active galactic nucleus (AGN), causes the centers of galaxies to temporarily outshine all the stars in their disks. While most observed radio transients last only a few days or weeks, this particular source has persisted for several years, marking it as the first known event of its kind. The findings were published in The Astrophysical Journal.
The study was spearheaded by Stephanie Komossa from MPIfR, joined by researchers from the Australia Telescope National Facility (ATNF), the Sydney Institute for Astronomy (SIfA), the Turin Astrophysical Observatory, the State Key Laboratory of Radio Astronomy and Technologies, the University of Science and Technology of China, the HUN-REN–ELTE Extragalactic Astrophysics Research Group, the Konkoly Observatory, the MTA Centre of Excellence, the Gemini Observatory, and several other universities.
Komossa and her team investigated SDSS J110546.07+145202.4 by combining fresh observations with archival data from multiple observatories across various wavelengths, spanning X-ray and optical data to radio and infrared. The supermassive black hole at the center of SDSS J110546.07+145202.4 has a relatively modest mass but is growing at an extraordinary rate through the accretion of matter in its disk. Based on the extensive dataset they analyzed, the team concluded that the black hole has been accreting material for several years, triggering the jet they observed.
“Bright radio emissions from rapidly growing, low-mass black holes are rare in themselves. Their shift into a long-lasting, radio-active state has never been observed before,” said Komossa. The reasons behind the supermassive black hole’s increased accretion of material and the prolonged duration of the flare remain unclear. However, follow-up observations using facilities like the Very Long Baseline Array (VLBA) could shed light on this mystery.
It is quite evident that this event serves as a prototype for a new class of galaxies exhibiting rapid changes in radio emissions. Such behavior, where a supermassive black hole accretes a large amount of matter and grows swiftly, is what astronomers expect to see in galaxies from the early Universe. Yet, this particular galaxy lies within the last 2 billion years of cosmic history, making it an exception. Its relative proximity also allows for detailed observations, which could lead to a better understanding of black hole physics, jet formation, and their evolution.
“High-energy events like this can provide astronomers with a wealth of valuable insights. By observing these jets and flares, we can study physical processes in the most extreme environments of the Universe,” said co-author Kovi Rose from the Sydney Institute for Astronomy. In the near future, according to Komossa, next-generation arrays such as the Square Kilometer Array (SKA) will come online, enabling us to learn even more about this unique discovery:
With precision telescopes like the upcoming SKA, we will be able to identify similar radio transients in future sky surveys. This is crucial for filling gaps in our understanding of the early Universe.
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