Cooling Flow
As the ICM in the core of many galaxy clusters is dense, it emits a lot of X-ray radiation (the emission is proportional to the density-squared). In the absence of heating, the ICM should be cooling. As it cools, hotter gas will flow in to replace it. This is known as a cooling flow. The cooling flow problem is the lack of evidence of cooling of the ICM.
Read more about this topic: Intracluster Medium
Famous quotes containing the words cooling and/or flow:
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—James Weldon Johnson (1871–1938)
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