Faint gas shells around ellipticals

Faint gas shells around ellipticals - Hot gas in clusters...

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Faint gas shells around ellipticals Ellipticals have faint gas shells that need massive "dark" haloes to contain them. The gas particles are moving too quickly (they are too hot) for the gravity of the visible matter to hang onto it. However, the number of ellipticals with these faint gas shells is too large to be only a temporary feature of ellipticals. The dark haloes must extend out to 300,000 light years around each galaxy. The extent of this dark matter pushes up to around 0.2. If the haloes are larger than originally thought, could approach Motion of galaxies in a cluster Galaxy cluster members are moving too fast to be gravitationally bound unless there is unseen mass. The reasonable assumption is that we do not live at a special time, so the galaxies in the cluster must have always been close to each other. The large velocities of the galaxies in the clusters are produced by more gravity force than can be explained with the gravity of the visible matter in the galaxies.
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Unformatted text preview: Hot gas in clusters The existence of HOT (i.e., fast moving) gas in galaxy clusters. To keep the gas bound to the cluster, there needs to be extra unseen mass. Quasar spectra Absorption lines from hydrogen in quasar spectra tells us that there is a lot of material between us and the quasars. Gravitational Lensing Gravitational lensing of the light from distant galaxies and quasars by closer galaxies or galaxy clusters enables us to calculate the amount of mass in the closer galaxy or galaxy cluster from the amount of bending of the light. The derived mass is greater than the amount of mass in the visible matter. Inventorying all of the ordinary matter in the lensing galaxy clusters (those that lens the light from distant galaxies) and comparing it to the total mass of the galaxy clusters gives a 5 to 1 ratio of dark matter to ordinary matter....
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