The Report to Science by Forbes, Beasley, Bekki, Brodie and Strader has been published online by Science Express and is currently scheduled to appear in print on August 29th.
The Swinburne University Media Release can be found here.
Please contact dforbes@swin.edu.au for further details.

Galaxy Disruption in a Halo of Dark Matter

Astronomers Assoc. Professor Forbes and Dr Beasley (Swinburne University of Technology) and Dr Bekki (University of New South Wales), along with US colleagues Professor Brodie and Mr Strader (University of California) have reported to the US journal Science their discovery of a dwarf satellite galaxy captured in the process of being disrupted in a halo of dark matter. Although long predicted, direct evidence for plumes of stars being ripped from a dwarf galaxy as it is swallowed up by a giant galaxy has remained elusive. This discovery provides the best evidence to date. The astronomers made this discovery using a new camera on the Hubble Space Telescope, and which was later confirmed using the Keck telescope in Hawaii. These observations also support the suggestion that dwarf galaxies can be transformed from one type into another during the disruption process.


Click on images for larger versions


Original Hubble Space Telescope image (top left), enhanced image (top right), simulated image (lower right), the nearby Andromeda galaxy and two satellites (lower left).

Original full sized Hubble Space Telescope image. The spiral galaxy, dwarf and plumes of stars can be seen in the lower left.

Enhanced Hubble Space Telescope image showing the edge-on spiral galaxy and the dwarf galaxy above it, at the centre of the plumes.

Smoothed colour image which better shows the plumes of stars ripped from the dwarf and a possible warp in the spiral galaxy on its lower left side.

Surface brightness, ellipticity and position angle profiles for the dwarf galaxy. The horizontal line represents the dwarf main body.

Central surface brightness vs magnitude. The disrupted dwarf is labelled ACS. Open symbols are dIrr and dE, filled symbols dSph galaxies.

Movie sequence showing the orbit and disruption of a dwarf satellite in a dark matter halo over 5 billion years. 10MB !

Sequence of snapshots showing the orbit a dwarf (blue) around a spiral (purple) galaxy. The timescale in billions of years (Gyr) is shown.



Contact details:
Assoc. Professor Duncan A. Forbes
Centre for Astrophysics & Supercomputing
Swinburne University of Technology
Hawthorn VIC 3122, Australia
Phone: +61 3 9214 4392, Mobile: +61 0404 171 540, Fax: +61 3 9214 8797, Email: dforbes@swin.edu.au
For details of the computer simulations, contact Dr Kenji Bekki (UNSW), phone: +61 2 9385 5572.
Hubble Space Telescope images courtesy of NASA and STScI.