Originally Posted by Garth
That is interesting ST. How dense is the inter-galactic-cluster medium?
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There are two main components to the intergalactic medium, the cold component (T<10
5 K) and the warm-hot component (10
5-10
7 K). The former is only a few times the critical density:
corresponding to a density of about 10
-5 cm
-3. The warm-hot component is about a factor of ten more dense than this. Finally, intracluster gas has densities of order 10
-3 cm
-3 and temperatures of around 10
7 K.
You can determine these conditions from a lot of things, including fitting absorption lines in quasar spectra, looking at X-ray emission and absorption, and the Sunyaev-Zeldovich effect.