A redshift survey of the nearby galaxy cluster Abell 2107: Global
  rotation of the cluster and its connection to large-scale structures in the
  universe
  We study the rotational motion of the galaxy cluster Abell 2107 at redshift z
= 0.04 and its connection to nearby large-scale structures using a large amount
of spectroscopic redshift data. By combining 978 new redshifts from the
MMT/Hectospec observations with data in the literature, we construct a large
sample of 1968 galaxies with measured redshifts at clustercentric radius $R <
60^\prime$. Our sample has high (80%) and spatially uniform completeness at
r-band apparent magnitude $m_{r,\textrm{Petro},0}$ < 19.1. We first apply the
caustic method to the sample and identify 285 member galaxies of Abell 2107 at
$R < 60^\prime$. Then the rotation amplitude and the position angle of rotation
axis are measured. We find that the member galaxies show strong global rotation
at $R < 20^\prime$ ($v_\textrm{rot}/\sigma_v$ ~0.6) with a significance of >
3.8$\sigma$, which is confirmed by two independent methods. The rotation
becomes weaker in outer regions. There are at least five filamentary structures
that are connected to the cluster and that consist of known galaxy groups.
These structures are smoothly connected to the cluster, which seem to be
inducing the global rotation of the cluster through inflow of galaxies.
