Article Posted on : - May 02, 2010

The largest atlas of nuclear galactic rings has been unveiled. A NASA, ESA Photo by D. Maoz, G. F. Benedict et al.

LONDON (PTI): Astrophysicists have unveiled what they claim is the largest atlas of nuclear galactic rings, which includes 113 rings in 107 galaxies.

"The Atlas of Images of Nuclear Rings (AINUR) is the most complete atlas of nuclear rings created to date," said co-author Sébastien Comerón of the Institute of Astrophysics of the Canary Islands.

The nuclear rings are ring-shaped, star-forming configurations located around galactic nuclei. They range in size on average from between 500 to 3,000 light years, and are very bright because they contain an abundance of young stars, including some extremely massive ones. This kind of star has a short lifetime but shines very brightly before a supernova.

To find the rings, the astrophysicists used images from around 500 galaxies observed by the Hubble Space Telescope, the 'Monthly Notices of the Royal Astronomical Society' reported.

The images were processed using filters, generating various kinds of maps to help identify the rings more easily.

"The AINUR atlas has also looked for relationships between the properties of the nuclear rings and those of the galaxies in which they are found, and we have been able to statistically prove that most rings are associated with Lindblad resonances (gravitational shoves that push objects out of certain orbits and into others)," Comeron said.

In the atlas, the astrophysicists have shown that when the rings are in a barred galaxy, the maximum radius that a nuclear ring can attain is 25 per cent of the length of the bar, and that the maximum radius is inversely proportional to the strength of the bar.

This is the behaviour that was predicted for the internal Lindblad resonances, which are determined by the size of the bar and their strength.