Fast and Furious starring Dual Quasars
5 April 2023
Astronomers describe 'cosmic noon' as a dramatic period in the history of our Universe when it was buzzing with galaxy mergers and furious star formation. Observing these mergers has been relatively rare and challenging since the Universe was very young - only three billion years old! Astronomers found evidence of such a ‘cosmic noon’ merger for the first time by detecting a pair of energetic quasars in the same galactic neighbourhood.
Galaxies grow and evolve by merging with other galaxies. When galaxies merge, they blend billions of stars, just like a ‘smoothie’. A lot of other stars can be born from that 'smoothie'. In some cases, these energetic blends can provide enough food for the supermassive black hole at its centre, making it so active that it releases bright, energetic electromagnetic radiation. Astronomers call such bright objects 'quasars'.
Using powerful ground and space-based telescopes, including NOIRLab’s Gemini North telescope in Hawai‘i, a team of astronomers found not one but two quasars very close to each other. They are only 10000 light-years apart! Researchers think these galaxies are on their way to merging into a giant elliptical galaxy.
Finding such a system of two supermassive black holes so close to each other in the early universe is quite tricky — it's just like finding a needle in a haystack. For one, it is difficult to tell the two black holes apart, and they need to be actively eating material and shining as quasars simultaneously, which is rare.
To verify their discovery, astronomers used the Gemini Multi-Object Spectrograph (GMOS) and GNIRS on the Gemini North telescope in Hawai‘i. These telescopes calculated how far they are from each other and confirmed that the two objects were both quasars.
Astronomers now look forward to studying in detail how galaxies evolve at cosmic noon, how supermassive black holes grow in the early universe, and how frequently galaxy mergers occur.
Image: This artist's impression of a closely bound duo of energetic quasars — the hallmark of a pair of merging galaxies — seen when the Universe was only three billion years old. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/M. Zamani, J. da Silva
Cool Fact
Galactic mergers can produce bright quasars that outshine the entire galaxy. Some of these mergers can become massive elliptical galaxies that contain black holes that are many billions of times the mass of our Sun. Data shows that for every 100 supermassive black holes, only one should be actively eating at a given time, making the discovery of these dual quasars extremely rare and fascinating!