A Galaxy Cluster Makes Its Mark (Forwarded)

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998

FOR RELEASE: September 11, 2008

A Galaxy Cluster Makes Its Mark

Abell 1689, shown in this composite image, is a massive cluster of galaxies
located about 2.3 billion light years away that shows signs of merging
activity. Hundred-million-degree gas detected by NASA's Chandra X-ray
Observatory is shown as purple in this image, while galaxies from optical
data from the Hubble Space Telescope are colored yellow. The X-ray emission
has a smooth appearance, unlike other merging systems such as the Bullet
Cluster or MACS J0025.4-1222. The temperature pattern across Abell 1689 is
more complicated, however, possibly requiring multiple structures with
different temperatures.

The long arcs in the optical image are caused by gravitational lensing of
background galaxies by matter in the galaxy cluster, the largest system of
such arcs ever found. Further studies of this cluster are needed to explain
the lack of agreement between mass estimates based on the X-ray data and on
the gravitational lensing. Previous work suggests that filament-like
structures of galaxies are located near Abell 1689 along our line-of-sight
to this cluster, which may bias mass estimates using gravitational lensing.

Additional information and images are available at:
http://chandra.harvard.edu/photo/2008/a1689/