Reconstructing Orbits of Galaxies in Extreme Regions (ROGER) II:
  reliability of projected phase-space in our understanding of galaxy
  populations
  We connect galaxy properties with their orbital classification by analysing a
sample of galaxies with stellar mass $M_{\star} \geq 10^{8.5}h^{-1}M_\odot$
residing in and around massive and isolated galaxy clusters with mass $M_{200}
> 10^{15}h^{-1}M_\odot$ at redshift $z=0$. The galaxy population is generated
by applying the semi-analytic model of galaxy formation SAG on the cosmological
simulation MultiDark Planck 2. We classify galaxies considering their real
orbits (3D) and their projected phase-space position using the ROGER code (2D).
We define five categories: cluster galaxies, galaxies that have recently fallen
into a cluster, backsplash galaxies, infalling galaxies, and interloper
galaxies. For each class, we analyse the $g-r$ colour, the specific star
formation rate (sSFR), and the stellar age, as a function of the stellar mass.
For the 3D classes, we find that cluster galaxies have the lowest sSFR, and are
the reddest and the oldest, as expected from environmental effects. Backsplash
galaxies have properties intermediate between the cluster and recent infaller
galaxies. For each 2D class, we find an important contamination by other
classes. We find it necessary to separate the galaxy populations in red and
blue to perform a more realistic analysis of the 2D data. For the red
population, the 2D results are in good agreement with the 3D predictions.
Nevertheless, when the blue population is considered, the 2D analysis only
provides reliable results for recent infallers, infalling galaxies and
interloper galaxies.
