London: 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 Sbastien Comern 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
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.