Astronomers use VLA to image doughnut-shaped torus surrounding the black hole at the core of Cygnus A galaxy
At the core of Cygnus A sits a black hole with 2.5 billion times greater mass than the Sun
A group of astronomers from the National Radio Astronomy Observatory (NRAO) and Liverpool John Moores University, England claim to have directly observed for the first time the doughnut-shaped torus at the core of Cygnus A galaxy.
According to the researchers, this dusty torus surrounds the supermassive black hole and accretion disk at the core of the galaxy, and was imaged using Karl G. Jansky Very Large Array (VLA).
A torus is one of the most remarkable features of active galactic nuclei (AGN). It is made up of dust and gas that feeds into the accretion disc.
The concept was first postulated about four decades ago, and is now used to explain how an object in the Universe can appear differently when observed from different angles.
A quasar that appears bright and intense when viewed face-on looks faint when observed through its torus of dusty gas.
"Evidence exists for such structures in nearby AGN of lower luminosity, but we've never before directly seen one in such a brightly-emitting radio galaxy," said Chris Carilli, of the NRAO.
In the current study, astronomers focused on Cygnus A, a powerful radio-emitting galaxy located in Cygnus constellation, about 760 million light-years from Earth.
Cygnus A is about 10 times closer to Earth than any other galaxy with a similar level of bright radio emission. At the core of Cygnus A sits a black hole with 2.5 billion times greater mass than the Sun.
Using VLA, Carilli and his colleagues team were able to directly observe the gas in Cygnus A's torus.
"It's really great to finally see direct evidence of something that we've long presumed should be there," Carilli said.
The observations enabled researchers to determine the radius of Cygnus A's torus - approximately 900 light-years.
The team now plans to use the Atacama Large Millimetre/submillimetre Array (ALMA) to accurately determine the composition and shape of the torus.
ALMA will enable astronomers to view Cygnus A's torus at specific wavelengths, revealing precise details about the composition of the dust present within the torus.
The research is published in The Astrophysical Journal Letters.