  In the current paradigm, red sequence galaxies are believed to have formed as
blue disk galaxies that subsequently had their star formation quenched. Since
red-sequence galaxies typically have an early-type morphology, the transition
from the blue to the red sequence also involves a morphological transformation.
In this paper we study the impact of transformation mechanisms that operate
only on satellite galaxies, such as strangulation, ram-pressure stripping and
galaxy harassment. Using a large galaxy group catalogue constructed from the
SDSS, we compare the colors and concentrations of satellites galaxies to those
of central galaxies of the same stellar mass, adopting the hypothesis that the
latter are the progenitors of the former. On average, satellites are redder and
more concentrated than central galaxies of the same stellar mass.
Central-satellite pairs that are matched in both stellar mass and color,
however, show no average concentration difference, indicating that the
transformation mechanisms affect color more than morphology. The color and
concentration differences of matched central-satellite pairs are completely
independent of the halo mass of the satellite galaxy, indicating that
satellite-specific transformation mechanisms are equally efficient in haloes of
all masses. This strongly favors strangulation as the main quenching mechanism
for satellite galaxies. Finally, we determine the relative importance of
satellite quenching for the build-up of the red sequence. We find that roughly
70 percent of red sequence satellite galaxies with a stellar mass of 10^9 Msun
had their star formation quenched as satellites. This drops rapidly to zero
with increasing stellar mass, indicating that a significant fraction of red
satellites were already quenched before they became a satellite.
