Redshift-distortions

Redshift maps have two principal distortions:

  1. Fingers of God: Radial stretching pointed at the observer. They come about because of random velocities in clusters of galaxies.
  2. Large over densities (walls) lead to a coherent "bulk" motion: Walls appear denser and fluffier, voids bigger and emptier.

    In this animation we repeatedly add and remove the effects of the local (so-called "peculiar") velocities of the galaxies. The more uniform picture shows the true positions; the "squeezed" one the positions an observer at the center would measure using redshift as a distance indicator.

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Last modified: T Mar 3 15:07:00 MET 2003