The feedback process can throttle the formation of new stars inside cluster galaxies, in a complex interaction between the black hole and the hot cluster gas. These poorly-understood cold fronts are probably relics of earlier galaxy cluster collisions, and can linger for billions of years. These instruments observe galaxy clusters by the fluctuations they create in microwave light from the very early universe.
The result is a map of hundreds of galaxy clusters, many of which are too far to be seen directly by the light they emit. The huge amount of dark matter in a galaxy cluster produces enough gravity to bend the path of light passing by. In addition, lensing lets astronomers map where the mass in a galaxy cluster is located. This gas shines brightly in X-ray light, and affects radio light shining through the cluster from more distant sources.
As a result, the plasma provides several independent ways to detect and study galaxy clusters. And finally we have the galaxies themselves, which may weigh in the least, but are still very important.
The largest galaxies in the universe live in clusters, and interactions between cluster galaxies are a laboratory for understanding how these huge monsters form.
In addition, the galaxies host supermassive black holes , which can have a profound effect on the whole galaxy cluster. The galaxy cluster Abell contains several hundred galaxies held together by their mutual gravity.
The cluster's hot gas and dark matter may be invisible in this image, but their mass forms a gravitational lens, distorting images of farther galaxies into smears of light.
Those supermassive black holes drive powerful jets of matter that can be larger than the galaxies themselves. The jets carve out bubbles in the material between galaxies, known as the intercluster medium ICM.
Heavyweights February 10, Running Out of Gas January 25, Galaxies, Galaxies, Galaxies August 31, Close Group March 28, Interlopers November 5, Four-Member Sextet September 28, Hot Halo June 21, Galactic Pile-Up May 15, Grand Spiral April 19, Sailing Through the Galaxies February 13, Galactic Lens July 22, Galactic Baubles April 14, Clusters also affect light from the cosmic microwave background travelling through the cluster via a process called the Sunyaev-Zel'dovich SZ effect, where the frequency of light is modified as it passes through the cluster.
Another method is to examine the effect a cluster has on light from galaxies behind the cluster. The large mass of the galaxy cluster bends light passing through the cluster by a process called "gravitational lensing". Depending on how close the light travels to the mass, this can be a strong effect, giving characteristic arcs of light, or a weak, where the shapes of many galaxies are slightly distorted. The basic properties of the universe affect how clusters form and grow over their lifetimes.
Therefore we can measure the properties of the universe do cosmology by studying clusters. The primary way this can be done is to count how many clusters there are of a particular mass as a function of the distance from us. As we look further away with telescopes we are also looking into the past of the universe, as light takes time to reach us. Therefore by counting clusters with particular ranges of mass and by looking at how they shape the 3-d large-scale structure, we study how clusters grow and evolve over the lifetime of the universe.
It will make several surveys of the sky in the X-ray band, allowing us to discover between 50 to thousand clusters of galaxies, in addition to many other astronomical objects. Large spectroscopic and imaging surveys will complement the X-ray observations. Analyses of the optical light emitted by the galaxies they host will complement the survey by assessing the distance of the objects and the epoch at which they are observed.
We will use this large sample of clusters to produce tight constraints on the cosmological properties of the universe.
Many physical processes are important in galaxy clusters. The physics of the dark matter is thought to be well understood, even though dark matter cannot be directly seen.
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