Abell 2142

Abell 2142 ( A2142 short ) is a massive, X-ray bright clusters of galaxies in the constellation Corona Borealis. It is the result of a presently ongoing merger of two galaxy clusters. The galaxy clusters extends a total of more than 6 million light-years and contains several hundred galaxies. Abell 2142 has a heliocentric redshift of about 0,090. This corresponds to a radial velocity of about 27000 km / s, resulting in a distance of about 1.2 billion light-years (370 Mpc ) results .. The cluster is dominated by two giant cD galaxies and is therefore in Klaasifikationsschema by Rood and Sastry as type B ( binary) classified. The radial velocities of the two central galaxies differ by the very large amount of 1650 km / s, which is interpreted as a further indication that actually takes place a process of merging galaxy clusters. The term Abell 2142 goes back to the entry in the Abell catalog, a catalog of galaxy clusters.

X-ray image

The picture above right was taken from Chandra with the Advanced CCD Imaging Spectrometer 0.3-10.0 keV (ACIS ) on 20 August 1999. It shows an area of 7.5 × 7.2 arcmin. Then the collision of two large clusters of galaxies can be seen. The bright central region is cooler than the surrounding, elongated clouds with a temperature of 70 million Kelvin to about 50 million Kelvin. All the moves in a thin "atmosphere" of 100 million Kelvin hot gas. The bright spot above the left is an active galaxy within the cluster.

Dynamics of the fusion of the pile

Abell 2142 has attracted some attention to itself, since it opens up the possibility to investigate the merging of galaxies in more detail. Galaxy clusters grow by attracting smaller groups and clusters. During the merger, the kinetic energy of the colliding objects heats the gas between the coincident clusters, resulting in a marked difference in the gas temperature. These differences provide information about the stage, the geometry and velocity of the merger. Accurate temperature map may provide various information about the nature of the underlying physical processes. Previous studies ( for example, by ROSAT or ASCA ) did not have the capabilities of Chandra and XMM -Newton and could not depict in detail the region.

With Chandra it has been possible to measure variations in the temperature, density and pressure with high resolution. "Now we can begin to understand the physics of such merging processes, which are among the most energetic events in the universe, " said Maxim Markevitch of the Harvard- Smithsonian Center for Astrophysics, leader of the international team that is involved in the analysis of the observations. " The pressure and density maps of the cluster show a sharp boundary, which may consist of a merger only in a moving environment."

The observed in Abell 2142 X-ray emissions are largely smooth and symmetrical, suggesting that the object is the result of the merger of two galaxy clusters is that we observe in stage least 1-2 billion years after the first meeting. It would be the observation of non-uniform X-ray emissions and clear shock fronts expected if an earlier stage of the merger would be present. Markevitch et al. have suggested that the central galaxy ( called G1) of more massive cluster with the former central galaxy (G2 ) is fused to the less massive cluster. The relatively cool central region suggests that the warming of the central core was not on the heating by shock fronts in earlier stages of the merger and this interacts instead with the surrounding gas.