Maunakea observatories discover three pairs of fusing supermassive black holes

A cosmic dance between two fusing star systems, each containing a supermassive black hole that feeds rapidly on so much material that it creates a phenomenon known as a quasar, is a rare find.

Astronomers have discovered several pairs of such fusing galaxies, as luminous “double” quasars, with three Maunakea observatories in Hawaii – Subaru Telescope, WM Keck Observatory and Gemini Observatory. These double quasars are so rare, a research team led by the Kavli Institute of Physics and Mathematics of the Universe at the University of Tokyo estimates only 0.3% of all known quasars have two supermassive black holes located on a collision course with each other,

The study published today in the August 26, 2020 issue of The Astrophysical Journal.

“Despite their rarity, they represent an important stage in the evolution of galaxies, where the central giant awakens, gains mass, and potentially affects the growth of its host system,” said Shenli Tang, a student at the University of Tokyo and co-author of the study.

Quasars are one of the brightest, most energetic objects known in the universe, driven by supermassive black holes that are millions to billions of times more massive than our Sun. When material revolves around a black hole in the center of a galaxy, it is heated to high temperatures, releasing so much light that the quasar can overwhelm its host system. This makes a fusing pair of galaxies with quasar activity difficult to detect; it is difficult to separate the light from the two quasars because they lie in such close proximity to each other. Also, observing a wide enough area of ​​the sky to capture these rare events in sufficient numbers is a challenge.

To overcome these obstacles, the team took advantage of a sensitive broad-based aerial survey using the Hyper Suprime-Cam (HSC) camera on the Subaru Telescope.

“To make our work easier, we began by looking at the 34,476 well-known quasars of the Sloan Digital Sky Survey with HSC imaging to identify those that have two (or more) distinct centers,” said lead author John Silverman of the Kavli Institute of Physics. and Mathematics of the Universe. “Honestly, we did not start looking for double quasars. We examined images of these bright quasars to determine in what type of galaxies they preferred to live, when we began to see cases with two optical sources in their centers where we only expected one. “

The team identified 421 potential cases. However, there was still the chance that many of these were not bona fide double quasars, but rather chance projections such as starlight from our own galaxy. Confirmation requires detailed analysis of the candidates’ light to search for definitive signs of two distinct quasars.

Using Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS) and Gemini Observatory’s Near-Infrared Integral Field Spectrometer, Silverman and his team identified three double quasars, two of which were previously unknown. Each object in the pair showed the signature gas moving at thousands of kilometers per second under the influence of a supermassive black hole.

The newly discovered double quasars demonstrate the promise of wide-area imaging combined with high-resolution spectroscopic observations to reveal these elusive objects, which are the key to a better understanding of the growth of galaxies and their supermassive black holes.