ASTRON 1F03 Quiz: Galaxies and Dark Matter
12 Apr 2016
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Other spiral galaxies have rotation curves similar to ours, allowing measurement of their mass. 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 or the binary in orbit. 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. The total needed is more than the sum of the dark matter associated with each galaxy. There is evidence for intracluster superhot gas (about 10 million k0 throughout clusters densest in the center. Likely mostly primordial = shattering of heavier elements. Not nearly enough to account for dark matter. This head-tail radio galaxy"s lobes are being swept back, probably because of interaction with intracluster gas.
