Closest pair of supermassive black holes as seen by MUSE

In this Picture of the Week we peer closer into the galaxy UGC 4211, where astronomers have discovered two supermassive black holes on the verge of merging, separated by just 750 lightyears — the closest to have been found to date using multiple wavelengths and less than half of the previous record. They used ESO’s Very Large Telescope (VLT), the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner, and other telescopes to detect the bright light produced as the black holes engulf material in their vicinity.

Both of the images shown here were made using data from the MUSE instrument on ESO’s VLT in Chile. The left image shows a classical view of this galaxy, with dust lanes obscuring starlight. The image on the right shows emission from oxygen, nitrogen and hydrogen in blue, green and red respectively. Red indicates areas of star formation, and the bright white central region indicates the presence of two supermassive black holes swallowing material from their surroundings.

Combining data from the VLT, ALMA and other telescopes, a team led by Michael Koss at Eureka Scientific in the US could identify these two black holes and study them in detail. These black holes likely found each other when their host galaxies collided and merged. Observing this system will help improve our understanding of how galaxies and their supermassive black holes grow as they merge.