Using the ESO’s Very Large Telescope astronomers have stared back in time and observed reservoirs of cool gas around early galaxies, a perfect larder allowing the growth of supermassive black holes.

Astronomers have spotted gas halos around the earliest galaxies — a food supply for supermassive black holes. These halos — seen as they were over 12.5 billion years ago — could explain how these cosmic monsters grew so rapidly during a period in the Universe’s history known as the Cosmic Dawn.

This image shows one of the gas halos newly observed with the MUSE instrument on ESO’s Very Large Telescope superimposed to an older image of a galaxy merger obtained with ALMA. The large-scale halo of hydrogen gas is shown in blue, while the ALMA data is shown in orange. The halo is bound to the galaxy, which contains a quasar at its centre. The faint, glowing hydrogen gas in the halo provides the perfect food source for the supermassive black hole at the centre of the quasar. The objects in this image are located at redshift 6.2, meaning they are being seen as they were 12.8 billion years ago. While quasars are bright, the gas reservoirs around them are much harder to observe. But MUSE could detect the faint glow of the hydrogen gas in the halos, allowing astronomers to finally reveal the food stashes that power supermassive black holes in the early Universe. ( ESO/Farina et al.; ALMA (ESO/NAOJ/NRAO), Decarli et al.)

“We are now able to demonstrate, for the first time, that primordial galaxies do have enough food in their environments to sustain both the growth of supermassive black holes and vigorous star formation,” says Emanuele Paolo Farina, of the Max Planck Institute for Astronomy in Heidelberg, Germany, who led the research published in the Astrophysical Journal. “This adds a fundamental piece to the puzzle that astronomers are building to picture how cosmic structures formed more than 12 billion years ago.”

The observation may answer the question of how supermassive black holes were able to grow so large so early on in the history of the Universe, a puzzle to astronomers for years.

“The presence of these early monsters, with masses several billion times the mass of our Sun, is a big mystery,” explains Farina, affiliated with the Max Planck Institute for Astrophysics in Garching bei München. It means that the first black holes — which likely formed from the collapse of the first stars — must have grown very fast. Yet, until these findings, astronomers had not spotted ‘black hole food’ — gas and dust — in large enough quantities to explain their burgeoning size.

This food shortage issue was further compounded by observations made with the Atacama Large Millimeter/submillimeter Array (ALMA). These previous findings had revealed that much of the dust and gas in these early galaxies had fuelled rapid star formation. Thus suggesting that there would be very little matter left over to feed a black hole up to supermassive status.