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ALMA scientists find pair of black holes dining together in nearby galaxy merger

SMU News

While studying a nearby pair of merging galaxies using the Atacama Large Millimeter/submillimeter Array (ALMA)— an international observatory co-operated by the U.S. National Science Foundation’s National Radio Astronomy Observatory (NRAO)— scientists discovered two supermassive black holes growing simultaneously near the center of the newly coalescing galaxy. These super-hungry giants are the closest together that scientists have ever observed in multiple wavelengths. What’s more, the new research reveals that binary black holes and the galaxy mergers that create them may be surprisingly commonplace in the Universe. The results of the new research were published in The Astrophysical Journal Letters, and presented in a press conference at the 241st meeting of the American Astronomical Society (AAS) in Seattle, Washington.

At just 500 million light-years away from Earth in the constellation Cancer, UGC4211 is an ideal candidate for studying the end stages of galaxy mergers, which occur more frequently in the distant Universe, and as a result, can be difficult to observe. When scientists used the highly sensitive 1.3mm receivers at ALMA to look deep into the merger’s active galactic nuclei— compact, highly luminous areas in galaxies caused by the accretion of matter around central black holes— they found not one, but two black holes gluttonously devouring the byproducts of the merger. Surprisingly, they were dining side-by-side with just 750 light-years between them.

“Since we can only detect these black holes when they are actively consuming matter and producing large luminosities, we search for binary active black holes. Sometimes, the light from these black holes is wiped out by dust in the post-merger galaxy, making them especially difficult to find,” said Krista Lynne Smith, an observational astrophysicist at SMU (Southern Methodist University) and co-author of the research. “However, light in the millimeter and radio wavelength regime can travel through this dust. Instruments like ALMA detect this light.” READ MORE