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Session 12 - Cosmology, Large-Scale Structure and Distance Scales.
Display session, Monday, June 10
Great Hall,
The infall fields surrounding galaxy clusters produce a distortion in redshift-space maps of the large scale structure: galaxies in the infall field are compressed to form an artifact transverse to the observer's line of sight. When many clusters are present, these artifacts may join up and form structures encircling the observer. The result is an effect resembling a bull's-eye.
Using a two-dimensional numerical simulation of galaxy clustering, with initial power spectrum of the form P(k) \propto k^0, we investigate what an observer would see in redshift space, as opposed to real space. To make the comparison more realistic, we simulate both a magnitude limit and a constant slice angle. The result is an enhanced ring of galaxies encircling the observer at a distance roughly corresponding to the distance at which the selection function peaks. This ring is largely an artifact, produced by the velocity flow distortions and enhanced by the selection function. There is no corresponding feature in real space.
