clustering in two dimensions

The only real research I did today was discuss two-dimensional measures of three-dimensional galaxy clustering with Antara Basu-Zych (Columbia). She measures what we usually call w(theta); I measure what we usually call wp(rp); we figured out the relation between these, which depends on the angular diameter distance and the volume per solid angle (that is, an integral of the volume element over redshift). The main subtlety is to decide whether you want your wp(rp) in comoving or proper units; this can get confusing because almost all volume calculations that are commonly done are done in comoving, whereas transverse calculations tend to be proper.

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