By combining multiple telescope observations and advanced modeling, a multinational team of astronomers has discovered an extremely rare triple quasar system – only the second such object ever found.
Quasars are powerful sources of energy that sit in the center of a galaxy, surrounding a black hole. In systems with multiple quasars, the bodies are held together by gravity and are believed to be the product of galaxies colliding.
It is very difficult to observe triplet quasar systems, because of observational limits that prevent researchers from differentiating multiple nearby bodies from one another at astronomical distances.
The team combined observations from ESO’s New Technology Telescope at La Silla, Chile, and from the Calar Alto Observatory in Spain with advanced modelling. This enabled them to find the quasar, labeled QQQ J1519+0627.
The light from this object has traveled 9 billion light years to reach us, which means the light was emitted when the Universe was only a third of its current age.
Advanced analysis confirmed that what the team found was indeed three distinct sources of quasar energy and that the phenomenon is extremely rare.
“Honing our observational and modeling skills and finding this rare stellar phenomenon will help us understand how cosmic structures assemble in our universe and the basic processes by which massive galaxies form,” said Dr Michele Fumagalli from Princeton University and Carnegie Observatories, senior author of a paper accepted for publication in the Monthly Notices of the Royal Astronomical Society (arXiv.org version).
Two members of the triplet are closer to each other than the third. This means that the system could have been formed by interaction between the two adjacent quasars, but was probably not triggered by interaction with the more-distant third quasar. Furthermore, no evidence was seen of any ultra-luminous inferred galaxies, which is where quasars are commonly found. As a result, the astronomers propose that this triplet quasar system is part of some larger structure that is still undergoing formation.
“Further study will help us figure out exactly how these quasars came to be and how rare their formation is,” said lead author Dr Emanuele Farina of the Universita degli Studi dell’Insubria and the Universit`a degli Studi di Milano-Bicocca.
Bibliographic information: Farina EP et al. 2013. Caught in the Act: Discovery of a Physical Quasar Triplet. Accepted for publication in MNRAS; arXiv: 1302.0849