  Galaxies can form in a sufficiently deep gravitational potential so that
efficient gas cooling occurs. We estimate that such potential is provided by a
halo of mass $M \gtsim M_{c} \approx 7.0 \times 10^{12} ~ (\Delta_{c}(z)
(1+z)^{3})^{-1/2} \Msun$, where $\Delta_{c}(z)$ is the mean overdensity of
spherically virialized objects formed at redshift $z$, and $M_{c} \approx 4.0
\times 10^{11} \Msun$ at $z = 0$. Based on this criterion, our galaxy samples
are constructed from cosmology simulation data by using HiFOF to select
subhalos in those FOF halos that are more massive than $M_{c}$. There are far
more dark subhalos than galaxy-hosting subhalos. Several tests against
observations have been performed to examine our galaxy samples, including the
differential galaxy mass functions, the galaxy space density, the projected two
point correlation functions (CF), the HODs, and the kinematic pair fractions.
These tests show good agreements. Based on the consistency with observations,
our galaxy sample is believed to correctly represent galaxies in real universe,
and can be used to study other unexplored galaxy properties.
