352 Clustering in the universe
Figure 12.5. The relative effect of the mean streamingv 12 (r)and pairwise velocity
dispersionσ 12 (r)on the shape of the contours ofξ(rp,π), seen through the model of
equation (12.7). While a high pairwise dispersion,σ 12 =700 km s−^1 independent of scale
is assumed (a reasonable approximation), the two cases of zero mean streaming (F=0)
and stable clustering (F=1) are considered in the infall model of Davis and Peebles [8].
Here the effect of the coherent motions is more evident than in the data plot of figure 12.4:
the contours ofξ(rp,π)are clearly compressed along theπdirection. This compression is
a measure of^0 m.^6 /b.