The effect of cosmic web filaments on the properties of groups and their
  central galaxies
  The nature versus nurture scenario in galaxy and group evolution is a
long-standing problem not yet fully understood on cosmological scales. We study
the properties of groups and their central galaxies in different large-scale
environments defined by the luminosity density field and the cosmic web
filaments. We use the luminosity density field constructed using 8 Mpc/h
smoothing to characterize the large-scale environments and the Bisous model to
extract the filamentary structures in different large-scale environments. We
find differences in the properties of central galaxies and their groups in and
outside of filaments at fixed halo and large-scale environments. In
high-density environments, the group mass function has higher number densities
in filaments compared to that outside of filaments towards the massive end. The
relation is opposite in low-density environments. At fixed group mass and
large-scale luminosity density, groups in filaments are slightly more luminous
and their central galaxies have redder colors, higher stellar masses, and lower
specific star formation rates than those outside of filaments. However, the
differences in central galaxy and group properties in and outside of filaments
are not clear in some group mass bins. We show that the differences in central
galaxy properties are due to the higher abundances of elliptical galaxies in
filaments. Filamentary structures in the cosmic web are not simply visual
associations of galaxies, but rather play an important role in shaping the
properties of groups and their central galaxies. The differences in central
galaxy and group properties in and outside of cosmic web filaments are not
simple effects related to large-scale environmental density. The results point
towards an efficient mechanism in cosmic web filaments which quench star
formation and transform central galaxy morphology from late to early types.
