Quantifying the coherent outflows of galaxies around voids in the SDSS
  DR7
  We report the detection, with a high level of confidence, of coherent
outflows around voids found in the seventh data release of the Sloan Digital
Sky Survey (SDSS DR7). In particular, we developed a robust <|cos theta|>
statistical test to quantify the strength of redshift-space distortions (RSD)
associated with extended coherent velocity fields. We consistently find that
the vector that joins void centers with galaxies that lie in shells around them
is more likely to be perpendicular to the line-of-sight than parallel to it.
This effect is clear evidence for the existence of outflows in the vicinity of
voids. We show that the RSD exist for a wide range of void radius and shell
thickness, but they are more evident in the largest voids in our sample. For
instance, we find that the <|cos theta|> for galaxies located in shells within
2 h^-1 Mpc from the edge of voids larger than 15 h^-1 Mpc deviates 3.81sigma
from uniformity. The measurements presented in this work provide useful
information to constrain cosmological parameters, in particular Omega_m and
Sigma_8.
