Deprojecting the quenching of star formation in and near clusters
  Using H_delta and D_n4000 as tracers of recent or ongoing efficient star
formation, we analyze the fraction of SDSS galaxies with recent or ongoing
efficient star formation (GORES) in the vicinity of 268 clusters. We confirm
the well-known segregation of star formation, and using Abel deprojection, we
find that the fraction of GORES increases linearly with physical radius and
then saturates. Moreover, we find that the fraction of GORES is modulated by
the absolute line-of-sight velocity (ALOSV): at all projected radii, higher
fractions of GORES are found in higher ALOSV galaxies. We model this velocity
modulation of GORES fraction using the particles in a hydrodynamical
cosmological simulation, which we classify into virialized, infalling and
backsplash according to their position in radial phase space at z=0. Our
simplest model, where the GORES fraction is only a function of class does not
produce an adequate fit to our observed GORES fraction in projected phase
space. On the other hand, assuming that in each class the fraction of GORES
rises linearly and then saturates, we are able to find well-fitting 3D models
of the fractions of GORES. In our best-fitting models, in comparison with 18%
in the virial cone and 13% in the virial sphere, GORES respectively account for
34% and 19% of the infalling and backsplash galaxies, and as much as 11% of the
virialized galaxies, possibly as a result of tidally induced star formation
from galaxy-galaxy interactions. At the virial radius, the fraction of GORES of
the backsplash population is much closer to that of the virialized population
than to that of the infalling galaxies. This suggests that the quenching of
efficient star formation is nearly complete in a single passage through the
cluster.
