'Natural cosmic lens' reveals distant galactic violence

Washington, Oct 21 : Using a natural cosmic lens, astronomers have gained a rare glimpse of the violent assembly of a young galaxy in the early Universe, which suggests that the galaxy has collided with another, feeding a supermassive black hole and triggering a tremendous burst of star formation.

The astronomers used the National Science Foundation's Very Large Array (VLA) radio telescope to look at a galaxy more than 12 billion light-years from Earth, seen as it was when the Universe was only about 15 percent of its current age.

Between this galaxy and Earth lies another distant galaxy, so perfectly aligned along the line of sight that its gravity bends the light and radio waves from the farther object into a circle, or "Einstein Ring."

This gravitational lens made it possible for the scientists to learn details of the young, distant galaxy that would have been unobtainable otherwise.

"Nature provided us with a magnifying glass to peer into the workings of a nascent galaxy, providing an exciting look at the violent, messy process of building galaxies in the early history of the Universe," said Dominik Riechers, who led this project at the Max Planck Institute for Astronomy in Germany.

The new picture of the distant galaxy, dubbed PSS J2322+1944, shows a massive reservoir of gas, 16,000 light-years in diameter, that contains the raw material for building new stars.

A supermassive black hole is voraciously eating material, and new stars are being born at the rate of nearly 700 Suns per year.

By comparison, our Milky Way Galaxy produces the equivalent of about 3-4 Suns per year.

According to the astronomers, the black hole appears to be near the edge, rather than at the center, of the giant gas reservoir, indicating that the galaxy has merged with another.

"This whole picture, of massive galaxies and supermassive black holes assembling themselves through major galaxy mergers so early in the Universe, is a new paradigm in galaxy formation. This gravitationally lensed system allows us to see this process in unprecedented detail," said Chris Carilli, of the National Radio Astronomy Observatory.

In 2003, astronomers studied PSS J2322+1944, finding the Einstein Ring by observing radio waves emitted by molecules of Carbon Monoxide (CO).

In the latest study, scientists painstakingly produced a physical model of the lensing intermediate galaxy.

By knowing the mass, structure and orientation of this galaxy, they could then deduce the details of how it bends the light and radio waves from the more-distant galaxy.

This allowed them to reconstruct a picture of the distant object.

ANI