Galaxies flowing in the oriented saddle frame of the cosmic web

Abstract

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