PHYS 1000 Lecture Notes - Lecture 16: Hubble Deep Field, Cartwheel Galaxy, Intracluster Medium
12 Feb 2018
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Document Summary
Another way to measure the average mass of galaxies in a cluster is to calculate how much mass is required to keep the cluster gravitationally bound. Galaxies need between 3 and 10 times more mass than can be observed to explain their rotation curves. The discrepancy is even larger in galaxy clusters, which need 10 to 100 times more mass. This is more than the sum of the dark matter associated with each galaxy. Upward of 90 percent of the mass in the universe is dark. There is evidence for intracluster superhot gas (more than 10 million k) throughout clusters, densest in the center. This head-tail (cid:396)adio gala(cid:454)(cid:455)"s lo(cid:271)es a(cid:396)e (cid:271)ei(cid:374)g swept (cid:271)a(cid:272)k, p(cid:396)o(cid:271)a(cid:271)l(cid:455) (cid:271)e(cid:272)ause of (cid:272)ollisio(cid:374)s with intracluster gas (diagram). It is believed this gas is mainly primordial dating from the very early days of the universe. This gas has as much matter (in some cases substantially more) as the visible stars.
