Dr. Ganna Ivashchenko

Redshift-space distortion

by Ganna Ivashchenko

Also available as: PDF, LaTeX.
Redshift-space distortions are distortions (stretching and flattening) of the galaxy (2D) two-point correlation function, and also power spectrum (which have to be spherically symmetric in isotropic Universe) caused by peculiar (non-Hubble) motions of galaxies. These distortions can be divided onto:
  • Finger of God effect — stretching of (or flattening of ) along the line of sight on non-linear (less then  Mpc) scales due to random velocities of galaxies (e.g. virial velocities inside clusters), as far as redshift measurement errors;
  • Kaiser effect (or -distortion) — flattening of (or stretching of ) along the line of sight on linear (more then ) due to the galaxies infall onto overdense regions.
There is also one more effect causing the distortions of and even in the real space — the so called geometric flattening.
Alternative definitions:
Ontology information:
Redshift-space distortion
Related papers: