Astronomers using ESO's very large telescope have observed fresh gas tanks around some of the earliest galaxies in the Universe. These gaseous halos are the perfect food for the supermassive black holes in the center of these galaxies, which are now seen as they were over 12.5 billion years ago. This food storage could explain how these cosmic monsters developed so quickly during a period in the history of the Universe known as the Cosmic Dawn.
"We are now able to demonstrate, for the first time, that primordial galaxies have enough food in their environment to support both the growth of supermassive black holes and the formation of vigorous stars," says Emanuele Paolo Farina, from the Max Planck Institute for Astronomy. in Heidelberg, Germany, who led the research published today in The Astrophysical Journal. "This adds a fundamental piece to the puzzle that astronomers are building to illustrate how cosmic structures were formed over 12 billion years ago."
This image shows one of the gas halos newly observed with the MUSE instrument on the very large ESO telescope superimposed on an older image of a galaxy fusion obtained with ALMA. The large scale halo of hydrogen gas is displayed in blue, while ALMA data is displayed in orange.
Credit: ESO / Farina et al .; ALMA (ESO / NAOJ / NRAO), Decarli et al.
Astronomers have wondered how supermassive black holes could get so big so early in the history of the Universe. "The presence of these first monsters, with masses several billion times greater than the mass of our Sun, is a great mystery", explains Farina, also affiliated to the Max Planck Institute for Astrophysics in Garching bei München. This means that the first black holes, which could have formed following the collapse of the first stars, must have developed very quickly. But, until now, astronomers have not spotted "black hole food" - gas and dust - in sufficient quantity to explain this rapid growth.
To further complicate matters, previous observations with ALMA, the Atacama Large Millimeter / submillimeter network, revealed a lot of dust and gas in these early galaxies that fueled the rapid formation of stars. These ALMA observations suggested that there might be little food left to feed a black hole.
To solve this mystery, Farina and her colleagues used the MUSE instrument on ESO's very large telescope in the Chilean Atacama Desert to study quasars - extremely bright objects powered by supermassive black holes found at center of massive galaxies. The study identified 31 quasars that are seen as over 12.5 billion years ago, when the Universe was still just an infant, about 870 million years old. It is one of the largest samples of quasars from the beginning of the history of the Universe to study.
Astronomers have discovered that 12 quasars are surrounded by huge gas tanks: halos of cool, dense hydrogen gas spanning 100,000 light years from central black holes and billions of times the mass of the Sun. The team, from Germany, the United States, Italy and Chile, also found that these gas halos were closely linked to galaxies, providing the perfect food source to support both the growth of supermassive black holes. and the formation of vigorous stars.
The research was made possible thanks to the superb sensitivity of MUSE, the Multi Unit Spectroscopic Explorer, on ESO's VLT, which, according to Farina, "changed the game" in the study of quasars. "In a few hours per target, we were able to immerse ourselves in the vicinity of the most massive and voracious black holes of the young universe," he adds. Although quasars are bright, the gas tanks surrounding them are much more difficult to observe. But MUSE was able to detect the faint glow of hydrogen gas in the halos, allowing astronomers to finally reveal the food reserves that fuel the supermassive black holes in the early Universe.
In the future, ESO's extremely large telescope will help scientists reveal even more detail about galaxies and supermassive black holes in the first two billion years after the Big Bang. "With the power of ELT, we will be able to dig even deeper into the early Universe to find many other gas nebulae," said Farina.
Emanuele Paolo Farina, Fabrizio Arrigoni-Battaia, Tiago Costa, Fabian Walter, Joseph F. Hennawi, Alyssa B. Drake, Roberto Decarli, Thales A. Gutcke, Chiara Mazzucchelli, Marcel Neeleman, Iskren Georgiev, Anna-Christina Eilers, Frederick B. Davies, Eduardo Bañados, Xiaohui Fan, Masafusa Onoue, Jan-Torge Schindler, Bram P. Venemans, Feige Wang, Jinyi Yang, Sebastian Rabien, Lorenzo Busoni. The REQUIEM Survey. I. A Search for Extended Lyα Nebular Emission Around 31 z > 5.7 Quasars. The Astrophysical Journal, 2019; 887 (2): 196 DOI: 10.3847/1538-4357/ab5847