Galaxies flowing in the oriented saddle frame of the cosmic web
  The strikingly anisotropic large-scale distribution of matter made of an
extended network of voids delimited by sheets, themselves segmented by
filaments, within which matter flows towards compact nodes where they
intersect, imprints its geometry on the dynamics of cosmic flows, ultimately
shaping the distribution of galaxies and the redshift evolution of their
properties. The (filament-type) saddle points of this cosmic web provide a
local frame in which to quantify the induced physical and morphological
evolution of galaxies on large scales. The properties of virtual galaxies
within the Horizon-AGN simulation are stacked in such a frame. The iso-contours
of the galactic number density, mass, specific star formation rate (sSFR),
kinematics and age are clearly aligned with the filament axis with steep
gradients perpendicular to the filaments. A comparison to a simulation without
feedback from active galactic nuclei (AGN) illustrates its impact on quenching
star formation of centrals away from the saddles. The redshift evolution of the
properties of galaxies and their age distribution are consistent with the
geometry of the bulk flow within that frame. They compare well with
expectations from constrained Gaussian random fields and the scaling with the
mass of non-linearity, modulo the redshift dependent impact of feedback
processes. Physical properties such as sSFR and kinematics seem not to depend
only on mean halo mass and density: the residuals trace the geometry of the
saddle, which could point to other environment-sensitive physical processes,
such as spin advection, and AGN feedback at high mass.
