Spectral decomposition of the stellar kinematics in the polar disk
  galaxy NGC 4650A
  Context. The prototype of Polar Ring Galaxies NGC 4650A contains two main
structural components, a central spheroid, which is the host galaxy, and an
extended polar disk. Both photometric and kinematic studies revealed that these
two components co-exist on two different planes within the central regions of
the galaxy. Aims. The aim of this work is to study the spectroscopic and
kinematic properties of the host galaxy and the polar disk in the central
regions of NGC 4650A by disentangling their contributions to the observed
galaxy spectrum.
  Methods. We applied the spectral decomposition technique introduced in
previous works to long-slit spectroscopic observations in the CaII triplet
region. We focused the analysis along the PA = 152 that corresponds to the
photometric minor axis of the host galaxy, where the superimposition of the two
components is more relevant and the spectral decomposition is necessary. We aim
to disentangle the stars that move in the equatorial plane of the host galaxy
from those that move in the meridan plane, which is along the polar disk.
  Results. We successfully disentangled the spectra of the two structural
components of NGC 4650A and measured their line-of-sight velocity and velocity
dispersion profiles, and the stellar content along PA = 152. The host galaxy
shows significant rotation along its photometric minor axis, indicating that
the gravitational potential is not axisymmetric. The polar disk shows a
kinematic decoupling: the inner regions counter-rotating with respect the
outer-regions and the host spheroid. This suggests a complex formation history
for the polar disk, characterised by mass accretion with decoupled angular
momenta.
