Most elliptical galaxies are 'like spirals'

The majority of 'elliptical' galaxies are not spherical but disc-shaped, resembling spiral galaxies such as our own Milky Way with the gas and dust removed, new observations suggest. The results come from Atlas3D, a survey of all 260 early-type ('elliptical' and 'lenticular') galaxies in a well-defined volume of the nearby universe. Atlas3D shows a much closer link between 'elliptical' galaxies and spiral galaxies than previously thought. The findings are likely to change our ideas of how galaxies form and see astronomy text-books rewritten. A report of the research, by the international Atlas3D team, is published in an upcoming issue of Monthly Notices of the Royal Astronomical Society . 'Because we rely on optical images, up until now it has been very difficult to separate discs of stars seen face-on from rounder, spherical balls of stars seen edge-on,' said Dr Michele Cappellari of Oxford University, a Royal Society Research Fellow who is the UK lead of the Atlas3D project. 'But because stars in a thin disc rotate much faster than those in a spheroid, obtaining maps of stellar motions for all elliptical galaxies in the sample, we have shown that out of these 66% are disc-like.' The findings suggest that the idea that galaxies can be clearly separated into two different 'families', spiral galaxies and elliptical galaxies, reflecting two distinct paths to galaxy formation, is inaccurate.