An observational detection of the bridge effect of void filaments
  The bridge effect of void filaments is a phrase coined by Park & Lee (2009b)
to explain the correlations found in a numerical experiment between the
luminosity of the void galaxies and the degree of the straightness of their
host filaments. Their numerical finding implies that a straight void filament
provides a narrow channel for the efficient transportation of gas and matter
particles from the surroundings into the void galaxies. Analyzing the Sloan
void catalog constructed by Pan et al (2012), we identify the filamentary
structures in void regions and determine the specific size of each void
filament as a measure of its straightness. To avoid possible spurious signals
caused by the Malmquist bias, we consider only those void filaments whose
redshifts are in the range of 0=< z <= 0.02 and find a clear tendency that the
void galaxies located in the more straight filaments are on average more
luminous, which is in qualitative agreement with the numerical prediction. It
is also shown that the strength of correlation increases with the number of the
member galaxies of the void filaments, which can be physically understood on
the grounds that the more stretched filaments can connect the dense
surroundings even to the galaxies located deep in the central parts of the
voids. This observational evidence may provide a key clue to the puzzling issue
of why the void galaxies have higher specific star formation rates and bluer
colors than their wall counterparts.
