Quasars control star formation

New simulations could explain oddly behaving gas

This is an artist’s impression of the quasar 3C 279. Astronomers connected the Atacama Pathfinder Experiment (APEX), in Chile, to the Submillimeter Array (SMA) in Hawaii, USA, and the Submillimeter Telescope (SMT) in Arizona, USA for the first time, to make the sharpest observations ever, of the centre of a distant galaxy, the bright quasar 3C 279. Quasars are the very bright centres of distant galaxies that are powered by supermassive black holes. This quasar contains a black hole with a mass about one billion times that of the Sun, and is so far from Earth that its light has taken more than 5 billion years to reach us. The team were able to probe scales of less than a light-year across the quasar — a remarkable achievement for a target that is billions of light-years away.

Distant quasars give us a way to view the very early Universe. Credit: ESO/M. Kornmesser

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Astronomers have been able to determine how quasars, galaxies with very active black holes at their centres, control star formation, and how they regulate the build up of galaxies.

Quasars are known to push the gas involved with star formation to the outer reaches of the Galaxy at unbelievably high speeds, but until now it’s remained a mystery as to how this is possible.

The researchers found that the gas is heated to a very high temperature – as high as tens of billions of degrees Celsius.

It’s heated by the energy released from supermassive black holes that are powering a quasar.

The build up of heat generates extremely high pressures, which eventually accelerates the hot gas to the outskirts of the Galaxy at speeds of 2000km per second.

As it gets further away from the black hole, the gas cools down for a short period of time, making it visible to radio telescopes.

“It is the first time that we have seen outflowing cold gas moving at these large speeds at such large distances from the supermassive black hole,” says Claudia Cicone, a PhD student at Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology.

“It is very difficult to have matter with temperatures this low move as fast as we observed.”

Powerful radio telescopes and supercomputer simulations gathered the data for the research, which came out of two teams from Cambridge University.

“We found that while gas is launched out of the quasar at very high temperatures, there is enough time for some of it to cool through radiative cooling – similar to how the Earth cools down on a cloudless night.” said Tiago Costa, a PhD student at the Institute of Astronomy.

Being one of the most luminous objects in the Universe, quasars can be seen many billions of light years away.

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This gives researchers a way to view the Universe as it was billions of years ago, during its early formation.