Understanding the shape of the galaxy two-point correlation function at
  z~1 in the COSMOS field
  We investigate how the shape of the galaxy two-point correlation function as
measured in the zCOSMOS survey depends on local environment, quantified in
terms of the density contrast on scales of 5 Mpc/h. We show that the flat shape
previously observed at redshifts between z=0.6 and z=1 can be explained by this
volume being simply 10% over-abundant in high-density environments, with
respect to a Universal density probability distribution function. When galaxies
corresponding to the top 10% tail of the distribution are excluded, the
measured w_p(r_p) steepens and becomes indistinguishable from LCDM predictions
on all scales. This is the same effect recognised by Abbas & Sheth in the SDSS
data at z~0 and explained as a natural consequence of halo-environment
correlations in a hierarchical scenario. Galaxies living in high-density
regions trace dark matter halos with typically higher masses, which are more
correlated. If the density probability distribution function of the sample is
particularly rich in high-density regions because of the variance introduced by
its finite size, this produces a distorted two-point correlation function. We
argue that this is the dominant effect responsible for the observed "peculiar"
clustering in the COSMOS field.
