Astronomers have discovered a quasar powered by a supermassive black hole in the infant universe. Strikingly, this quasar appears to emit molecular gas, the raw material for new stars to form.
The discovery helps confirm theories that star formation in some galaxies has slowed to an almost complete halt.
The quasar, named J2054-0005, was observed by the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile. We see this as it was about 12.8 billion years ago, when the age of the universe was less than 1 billion years.
Quasar, short for “quasi-stellar radio source,” is the name given to compact regions at the heart of some active galaxies where a feeding supermassive black hole superheats surrounding matter and ejects powerful jets of that matter, resulting in incredibly bright emissions of light.
Quasars, which occur as point-like sources of light-like stars, can be used to probe conditions found in the early universe when seen from very long distances. Such regions have long been suspected to strongly influence the galaxies surrounding them, but scientists say this is the first time we have seen solid evidence of suppression of star formation driven by the outflow of molecular gas in an early quasar-hosted universe. galaxy.
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Stars form in vast clouds of molecular gas when a small region becomes too dense and collapses under its own gravity. This blob of prestellar gas continues to accumulate mass from the cloud and eventually becomes a protostar. The protostar continues to accumulate gas and grow until it is large enough to trigger the nuclear fusion of hydrogen into helium in its core, the process that defines a full-fledged star.
The richer a galaxy is in molecular gas, the more densely it can give birth to high concentrations of stars, leading to the production of large numbers of stars in periods called “starbursts”. Conversely, if this gas is pushed out of the galaxy into intergalactic space faster than it can be consumed by the star formation process, these so-called molecular outflows suppress star formation.
“Theoretical work shows that molecular gas outflows play an important role in the formation and evolution of galaxies from an early age because they can regulate star formation,” Dragan Salak, co-leader of the team and an assistant professor at Hokkaido University, said in a statement. said. . “Quarsars are particularly powerful sources of energy, so we expected they could produce strong outputs.”
In the shadow of a quasar
According to Takuya Hashimoto, co-leader of the team and an assistant professor at the University of Tsukuba, J2054-0005 was chosen as the observational target to investigate these outflows and their effects because it is one of the brightest quasars in the very distant universe.
Meanwhile, ALMA, which consists of 66 high-sensitivity antennas in a single telescope, was chosen to observe J2054-0005 because the team believes it is the only telescope in the world with sufficient sensitivity and frequency coverage to detect the molecular gas outflows of the targeted quasar.
The team discovered the outflowing molecular gas through light absorption patterns; This means that the researchers did not see the microwave radiation coming directly from the bound molecules of oxygen and hydrogen atoms or the “hydroxide” (OH) molecules that make up it.
“Instead, we observed radiation from the bright quasar, and absorption means that the OH molecules absorbed some of the radiation from the quasar,” Salak said. “So it was like revealing the presence of a gas by seeing the ‘shadow’ it casts in front of the light source.”
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The team’s findings represent the first strong evidence of molecular outflows from quasars in the early universe, thus confirming how star formation slowed down during cosmic infancy.
“Molecular gas is a very important component of galaxies because it is the fuel for star formation,” Salak concluded. “Our findings suggest that quasars can suppress star formation in their host galaxies by spewing molecular gas into intergalactic space.”
The team’s research was published in The Astrophysical Journal.