Most distant quasar discovered shines a light on black hole growth

A team of astronomers led by the University of Arizona observed a luminous quasar 13.03 billion light years from Earth – the most distant quasar discovered to date. Dating back to 670 million years after the Big Bang, when the universe was only 5% of its current age, the quasar hosts a supermassive black hole equivalent to the combined mass of 1.6 billion suns.

As well as being the most distant – and by extension, the oldest – known quasar, the object is the first of its kind to show evidence of an outgoing wind of superheated gas escaping from the vicinity of the black hole at one-fifth the speed of light. In addition to revealing a strong wind driven by a quasar, the new observations also show intense star-forming activity in the host galaxy where the quasar is located, officially designated J0313-1806.

The researchers will present their results, which have been accepted for publication in Letters from the Astrophysical Journal, at a press conference and scientific conference at the 237th meeting of the American Astronomical Society, which will be held virtually Jan. 11-15.

The previous record holder among the quasars of the infantile universe was discovered three years ago. The UArizona team also contributed to this discovery. Quasars are thought to result from supermassive black holes engulfing surrounding matter, like gas or even entire stars, resulting in a maelstrom of superheated matter known as an accretion disk that swirls around the black hole. Because of the enormous energies involved, quasars are among the brightest sources in the cosmos, often surpassing their host galaxies.

Although J0313-1806 is only 20 million light-years older than the former record holder, the new quasar contains a supermassive black hole twice the size. This marks a significant breakthrough for cosmology, as it constitutes the strongest constraint to date on the formation of black holes in the early universe.

“This is the first evidence of how a supermassive black hole affects its host galaxy around it,” said lead author of the paper Feige Wang, a Hubble member of the UArizona Steward’s Observatory. “From observations of less distant galaxies, we know it has to happen, but we’ve never seen it happen so early in the universe.”

The quasars that already amassed millions, if not billions, of solar masses in their black holes in a time when the universe was very young pose a challenge to scientists who try to explain how they came to be as they barely had time to do so. A commonly accepted explanation for the formation of a black hole involves a star exploding as a supernova at the end of its life and collapsing into a black hole. When these black holes merge over time, they can – in theory – turn into supermassive black holes. However, just as it would take many lifetimes to build up a retirement fund by piercing a dollar each year, quasars in the early universe are much like millionaires at a young age; they must have acquired their mass by other means.

The newly discovered quasar provides a new benchmark by excluding two current models of the formation of supermassive black holes in such short time frames. In the first model, massive stars made up largely of hydrogen and devoid of most of the other elements that make up later stars, including metals, form the first generation of stars in a young galaxy and provide the food for the nascent black hole. The second model involves dense star clusters, which collapse into a massive black hole from the start.

Quasar J0313-1806, however, has a black hole that is too massive to be explained by the aforementioned scenarios, according to the team that discovered it. The team calculated that if the black hole at its center formed as early as 100 million years after the Big Bang and grew as fast as possible, it still should have had at least 10,000 solar masses to start.

“This tells you that whatever you do, this black hole’s seed must have been formed by a different mechanism,” said co-author Xiaohui Fan, regent professor and associate head of the Arizona Department of Astronomy. “In this case, one that involves large amounts of primordial, cold hydrogen gas collapsing directly into a black seed hole.”

Because this mechanism does not require full stars as raw material, it is the only one that would allow the supermassive black hole of quasar J0313-1806 to grow up to 1.6 billion solar masses at such an early time. In the universe. This is what makes the new quasi-record so valuable, Fan explained.

“Once you move down to lower redshifts, any model could explain the existence of these less distant and less massive quasars,” he said. “For the black hole to reach the size we see with J0313-1806, it would have had to start with a seed black hole of at least 10,000 solar masses, and that would only be possible in the scenario d ‘direct collapse. “

The newly discovered quasar appears to offer a rare glimpse into the life of a galaxy at the dawn of the universe as many galaxy-forming processes that have since slowed down or ceased in galaxies that have existed for much longer still beat their full. .

According to current models of galaxy evolution, supermassive black holes growing in their centers could be the main reason why galaxies eventually stop making new stars. Acting like a blowtorch of cosmic proportions, quasars ferociously explode their surroundings, effectively sweeping their host galaxy with much of the cold gas that serves as the raw material from which stars are formed.

“We believe these supermassive black holes were the reason many large galaxies stopped forming stars at some point,” Fan said. “We are seeing this ‘extinction’ at lower redshifts, but until now we had no idea how far this process began in the history of the universe. This quasar is the first evidence that extinction may have taken place very early.

By measuring the brightness of the quasar, Wang’s team calculated that the supermassive black hole at its center ingests the mass equivalent of 25 suns per year, on average, which is believed to be the main reason for its plasma wind. hot at high speed blowing the galaxy around it at a relativistic speed. For comparison, the black hole in the center of the Milky Way has essentially become dormant.

And while the Milky Way forms stars at a leisurely pace of about one solar mass each year, J0313-1806 produces 200 solar masses during the same period.

“This is a relatively high rate of star formation, similar to that seen in other quasars of similar age, and it tells us that the host galaxy is growing very rapidly,” Wang said.

“These quasars are probably still building their supermassive black holes,” Fan added. “Over time, the flow of the quasar heats up and pushes all the gas out of the galaxy, then the black hole has nothing to eat and will stop growing. This is proof of the growth of these first massive galaxies and their quasars.

Researchers expect to find a few more quasars from the same time frame, including potential new records, said Jinyi Yang, the report’s second author, who is a Peter A. Strittmatter Fellow at Steward Observatory. Yang and Fan were using a 6.5-meter Magellan Baade telescopic handler to observe Las Campanas Observatory in Chile the night J0313-1806 was discovered.

“Our quasar survey covers a very wide field, allowing us to scan almost half of the sky,” Yang said. “We have selected more candidates who we will follow up on with more detailed observations.”

Researchers hope to uncover more of the secrets of the quasar through future observations, particularly with NASA’s James Webb Space Telescope, which is currently slated for launch in 2021.

“With telescopes on the ground, we can only see a point source,” Wang said. “Future observations could help solve the quasar in more detail, show the structure of its flow and how far the wind extends in its galaxy, and that would give us a much better idea of ​​its stage of evolution.”