Mock Galaxy Catalogues And Their Application To Future Galaxy Surveys

Abstract

We present a method for constructing end-to-end mock galaxy catalogues using a semi-analytical model of galaxy formation, applied to the halo
merger trees extracted from a cosmological N-body simulation. These
mocks are lightcone catalogues, which incorporate the evolution of galaxy properties with cosmic time. Interpolation is used to
determine the epoch at which a galaxy will appear in the past
lightcone of the observer. We discuss several applications of mock
catalogues. Firstly, we consider the effectiveness of the BzK colour
selection technique. The mock catalogue predictions are in reasonable
agreement with the observed number counts of BzK galaxies. We predict
that over 75 per cent of the model galaxies with K≤23, and redshift 1.4<z<2.5, are selected by the
BzK technique. Interloper galaxies, outside the target redshift range,
are predicted to dominate bright samples of BzK galaxies (i.e. with
K≤21). Fainter K-band cuts are
necessary to reduce the predicted interloper fraction. Secondly, we
use a mock catalogue to calibrate a galaxy group-finding algorithm,
via an objective method based upon the recovery of the distributions
of several, easily measurable group properties. We find that it is
extremely difficult to determine unique values for the linking lengths
by minimising the χ^2 statistic for individual properties, and
that it is necessary to combine χ^2 for more than one group
property to reduce the parameter space. However, based upon our
calibration, we conclude that the optimal linking lengths depend upon
the multiplicity of the groups and the group property that one wishes to recover. For our final application, we use a lightcone catalogue to
estimate the cosmology-independent angular correlation function,
ω(θ), for samples of galaxies, selected in bins of
apparent magnitude, in a thin redshift slice comparable to the size of
photometric redshift errors. We compare our estimates of
ω(θ) with the GALFORM predictions of the 3-dimensional
real-space and redshift-space correlation functions. The amplitude of
the real-space and redshift-space correlation functions display a
trend with increasing luminosity. However, this trend is less clear in
ω(θ) due to noisy estimates for the brightest two apparent
magnitudes bins.