Distances to Galaxies

Distances to Galaxies - Distances to Galaxies Some stars in...

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Distances to Galaxies Some stars in a far away galaxy are moving toward us, so their absorption lines will be blueshifted. Other stars will have redshifted lines because they are moving away from us. The resulting spectral lines from the entire galaxy blend together to form a FAT line. The same effect is seen with the gas motions (caused by heat and rotation) inside a single star or gas cloud in our galaxy. The more random motion there is in an elliptical galaxy, the greater the spread in the distribution of velocities and the fatter the resulting galaxy spectral lines will be. More massive galaxies have more gravity so their stars are accelerated to faster orbital speeds. More massive galaxies should have broader lines and if the luminosity correlates with the mass, the more massive galaxies should have greater luminosity. Sandra Faber and Robert Jackson discovered in 1976 a simple relation between the spread of velocities (called the velocity dispersion ) and the luminosity of elliptical galaxies. For the inner
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This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

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Distances to Galaxies - Distances to Galaxies Some stars in...

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