Since the discovery of supermassive black holes in the early universe, with masses up to several hundred million times that of the sun, understanding how supermassive black holes formed and grew in the short period of time after the birth of the universe (less than a billion years) has puzzled astronomers. Theoretically, a black hole first begins to grow rapidly by expelling surrounding materials of the gas and dust at the centre of a dusty starburst galaxy, and the powerful energy generated in the process blows away the surrounding materials, finally transitioning into a quasar, which is observed as a very luminous, compact object.

Dusty starburst galaxies and the post-transition luminous quasars have been discovered only 700-800 million years after the Big Bang, and the existence of supermassive black holes has been known from observations of the luminous quasars. However, the "young" quasar in transition, which connects the two and holds the key to understanding their rapid growth in a similar period of the early universe, has not been found until now.

An international research team, coordinated by astronomer Seiji Fujimoto of the University of Copenhagen, with the participation, among others, of researchers from the Department of Physics of Sapienza University of Rome and the Italian National Institute of Astrophysics - INAF, has reanalysed a large amount of archival data from the Hubble Space Telescope and discovered an object, later named GNz7q, which is the missing link between starburst galaxies and luminous quasars in the early universe. The results of the work have been published in the journal Nature. 

Spectroscopic observations with radio telescopes show that GNz7q came into existence only 750 million years after the Big Bang. These observations were then compared with theoretical models. This important phase of the work was carried out by Rosa Valiante of INAF and Raffaella Schneider of Sapienza University of Rome and showed how the characteristics of the electromagnetic spectrum of this object, from X-rays to radio waves, do not differ from the predictions of the theoretical simulations.

 "This suggests that GNz7q is the first example of a rapidly growing black hole in the dusty center of an actively star-forming galaxy," says Schneider and Valiante. "We think GNz7q is a precursor to the supermassive black holes found in the early universe."

Not only is GNz7q an important stepping stone to understanding the origin of supermassive black holes, but the fact that this discovery was made in the GOODS-North region, one of the most well-studied sky regions in the night sky to date, has also surprised astronomers. GOODS, Great Observatories Origins Deep Survey, is astronomically investigated by the most powerful telescopes ever built (i.e. those operating in space such as ESA's Hubble, Herschel and XMM-Newton, NASA's Spitzer telescope and Chandra X-ray Observatory, as well as powerful ground-based telescopes, including the Subaru telescope) - suggesting that such sources may be more frequent than previously thought.

The research group aims to conduct a systematic search for similar sources using high-resolution observational campaigns and to use the NASA/ESA/CSA James Webb Space Telescope, once in regular operation, to study objects such as GNz7q with an unprecedented wealth of detail.

References:

Fujimoto et al. 2022, Nature, DOI 10.1038/s41586-022-04454-1

Further Information

Raffaella Schneider 
Department of Physics
raffaella.schneider@uniroma1.it