Tuesday, November 25, 2008

Strangled spiral galaxies

Image credit: M. Barden, C. Wolf, M. Gray and the STAGES team

These images of galaxies from the STAGES survey show how a newly discovered population of red spiral galaxies on the outskirts of crowded regions in the Universe may be a missing link in our understanding of galaxy evolution.

Large numbers of these "red spirals" were uncovered independently by two UK-led international collaborations: Galaxy Zoo, which uses volunteers from the general public to classify enormous numbers of galaxies; and STAGES, which uses images from the Hubble Space Telescope to look in detail at the Abell 901/902 supercluster system.

The red spiral galaxies (centre) are still disk-like and recognizably spiral in shape, their spiral arms are smooth than "normal" spiral galaxies (left). Furthermore, their colour is as red as seen in old elliptical galaxies (right). Astronomers from both teams believe these red spirals are objects in transition, where star formation has been shut off by interactions with its environment.

The STAGES results are led by Christian Wolf and will appear in a forthcoming issue of the Monthly Notices of the Royal Astronomical Society.