A Bound Violation on the Galaxy Group Scale: The Turn-Around Radius of
  NGC 5353/4
  The first observational evidence for the violation of the maximum turn-around
radius on the galaxy group scale is presented. The NGC 5353/4 group is chosen
as an ideal target for our investigation of the bound-violation because of its
proximity, low-density environment, optimal mass scale, and existence of a
nearby thin straight filament. Using the observational data on the
line-of-sight velocities and three-dimensional distances of the filament
galaxies located in the bound zone of the NGC 5353/4 group, we construct their
radial velocity profile as a function of separation distance from the group
center and then compare it to the analytic formula obtained empirically by
Falco et al. (2014) to find the best-fit value of an adjustable parameter with
the help of the maximum likelihood method. The turn-around radius of NGC 5353/4
is determined to be the separation distance where the adjusted analytic formula
for the radial velocity profile yields zero. The estimated turn-around radius
of NGC 5353/4 turns out to substantially exceed the upper limit predicted by
the spherical model based on the LambdaCDM cosmology. Even when the restrictive
condition of spherical symmetry is released, the estimated value is found to be
only marginally consistent with the LambdaCDM expectation.
