Discovery of the kinematic alignment of early-type galaxies in the Virgo
  cluster
  Using the kinematic position angles (PA_kin), an accurate indicator for the
spin axis of a galaxy, obtained from the ATLAS3D integral-field-unit (IFU)
spectroscopic data, we discovered that 57 Virgo early-type galaxies tend to
prefer the specific PA_kin values of 20 degree and 100 degree, suggesting that
they are kinematically aligned with each other. These kinematic alignment
angles are further associated with the directions of the two distinct axes of
the Virgo cluster extending east-west and north-south, strongly suggesting that
the two distinct axes are the filamentary structures within the cluster as a
trace of infall patterns of galaxies. Given that the spin axis of a massive
early-type galaxy does not change easily even in clusters from the hydrodynamic
simulations, Virgo early-type galaxies are likely to fall into the cluster
along the filamentary structures while maintaining their angular momentum. This
implies that many early-type galaxies in clusters are formed in filaments via
major mergers before subsequently falling into the cluster. Investigating the
kinematic alignment in other clusters will allow us to understand the formation
of galaxy clusters and early-type galaxies.
