Models for the Clustering of Far-Infrared and Sub-millimetre selected
  Galaxies
  We discuss and compare two alternative models for the two-point angular
correlation function of galaxies detected through the sub-millimetre emission
using the Herschel Space Observatory. The first, now-standard Halo Model, which
represents the angular correlations as arising from one-halo and two-halo
contributions, is flexible but complex and rather unwieldy. The second model is
based on a much simpler approach: we incorporate a fitting function method to
estimate the matter correlation function with approximate model of the bias
inferred from the estimated redshift distribution to find the galaxy angular
correlation function. We find that both models give a good account of the shape
of the correlation functions obtained from published preliminary studies of the
HerMES and H-ATLAS surveys performed using Herschel, and yield consistent
estimates of the minimum halo mass within which the sub-millimetre galaxies
must reside. We note also that both models predict an inflection in the
correlation function at intermediate angular scales, so the presence of the
feature in the measured correlation function does not unambiguously indicate
the presence of intra-halo correlations. The primary barrier to more detailed
interpretation of these clustering measurements lies in the substantial
uncertainty surrounding the redshift distribution of the sources.
