Connections between galaxy properties and halo formation time in the
  cosmic web
  By linking galaxies in Sloan Digital Sky Survey (SDSS) to subhaloes in the
ELUCID simulation, we investigate the relation between subhalo formation time
and the galaxy properties, and the dependence of galaxy properties on the
cosmic web environment. We find that central and satellite subhaloes have
different formation time, where satellite subhaloes are older than central
subhaloes at fixed mass. At fixed mass, the galaxy stellar-to-subhalo mass
ratio is a good proxy of the subhalo formation time, and increases with the
subhalo formation redshifts, especially for massive galaxies. The subhalo
formation time is dependent on the cosmic web environment. For central
subhaloes, there is a characteristic subhalo mass of $\sim 10^{12} \msun$,
below which subhaloes in knots are older than subhaloes of the same mass in
filaments, sheets, or voids, while above which it reverses. The cosmic web
environmental dependence of stellar-to-subhalo mass ratio is similar to that of
the subhalo formation time. For centrals, there is a characteristic subhalo
mass of $\sim 10^{12} \msun$, below which the stellar-to-subhalo mass ratio is
higher in knots than in filaments, sheets and voids, above which it reverses.
Galaxies in knots have redder colors below $10^{12} \msun$, while above
$10^{12} \msun$, the environmental dependence vanishes. Satellite fraction is
strongly dependent on the cosmic web environment, and decreases from knots to
filaments to sheets to voids, especially for low-mass galaxies.
