# Redshift and shapes of galaxies

How does peculiar velocities lead to the observed elongation of galaxy clusters in redshift space, otherwise known as the Fingers of God effect? I have read the relevant Wikipedia page, but cannot understand exactly how it works.

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Just a note on the title - the effect is on shapes of galaxy clusters, not the galaxies themselves. –  Chris White Feb 6 '13 at 16:13

The galaxies will only show an additional redshift (of say $\pm \Delta R$) if there is a component of their velocity along our line of sight. Hence the only direction the galaxy can be seemingly elongated is radially (i.e., along our line of sight to the galaxy), which is why the galaxies seem to be "pointing" at us. Which led to the name. :)