From voids to filaments: environmental transformations of galaxies in
  the SDSS
  We investigate the impact of filament and void environments on galaxies,
looking for residual effects beyond the known relations with environment
density. We quantified the host environment of galaxies as the distance to the
spine of the nearest filament, and compared various galaxy properties within 12
bins of this distance. We considered galaxies up to 10 $h^{-1}$Mpc from
filaments, i.e. deep inside voids. The filaments were defined by a point
process (the Bisous model) from the Sloan Digital Sky Survey data release 10.
In order to remove the dependence of galaxy properties on the environment
density and redshift, we applied weighting to normalise the corresponding
distributions of galaxy populations in each bin. After the normalisation with
respect to environment density and redshift, several residual dependencies of
galaxy properties still remain. Most notable is the trend of morphology
transformations, resulting in a higher elliptical-to-spiral ratio while moving
from voids towards filament spines, bringing along a corresponding increase in
the $g-i$ colour index and a decrease in star formation rate. After separating
elliptical and spiral subsamples, some of the colour index and star formation
rate evolution still remains. The mentioned trends are characteristic only for
galaxies brighter than about $M_{r} = -20$ mag. Unlike some other recent
studies, we do not witness an increase in the galaxy stellar mass while
approaching filaments. The detected transformations can be explained by an
increase in the galaxy-galaxy merger rate and/or the cut-off of extragalactic
gas supplies (starvation) near and inside filaments. Unlike voids, large-scale
galaxy filaments are not a mere density enhancement, but have their own
specific impact on the constituent galaxies, reducing the star formation rate
and raising the chances of elliptical morphology also at a fixed environment
density level.
