Chandra Catches Early Phase of Cosmic Assembly
Chandra's image of the galaxy cluster Abell 2125 reveals a complex of several massive multimillion-degree-Celsius gas clouds in the process of merging. Ten of the point-like sources are associated with galaxies in the cluster, and the rest are probably distant background galaxies. The small bright feature in the extreme lower right-hand corner is probably a background galaxy cluster not associated with Abell 2125.
The bright gas cloud on the upper left is the core of the cluster and envelops hundreds of galaxies. It consists of several elongated clouds that are merging. Chandra, Hubble Space Telescope, and Very Large Array radio telescope data show that several galaxies in the Abell 2125 core cluster are being stripped of their gas as they fall through surrounding high-pressure hot gas. (See C153 image). This stripping process has enriched the core cluster's gas in heavy elements such as iron.
In contrast, the bright large cloud on the lower right envelops hundreds of galaxies and has an extraordinarily low concentration of iron atoms. It is thought that this cloud, which is several million light years from the core cluster, has not yet been enriched by the stripping of iron-rich gas from its member galaxies. Over time, as this cloud merges into the core and the hot gas pressure increases, iron atoms should be swept from the galaxies.
Building a massive galaxy cluster is a step-by-step enterprise that takes billions of years and affects the growth and evolution of the member galaxies. The observations of Abell 2125 provide a rare glimpse into the early steps in this process.