Kinematics and physical properties of the nearby galaxy NGC 4656 and its
  TDG candidate
  Interacting galaxies provide us with an excellent laboratory for studying a
number of physical phenomena associated with these processes. In this paper, we
present a spectroscopic and kinematic analysis of the interacting galaxy NGC
4656 and its companion Tidal Dwarf Galaxy (TDG) candidate, NGC 4656UV. Using
Fabry-Perot and GMOS multi-slit data, we investigated the possible origin of
NGC 4656UV. We found that NGC 4656UV has a low metallicity
(12+log(O/H)$\sim$8.2) and it follows the mass-metallicity relation (MZR) for
normal dwarf galaxies. For NGC 4656, we estimated a flat oxygen abundance
gradient of $\beta$ = -0.027$\pm$0.029 dex kpc$^{-1}$, which suggests the
presence of gas flows induced by gravitational interactions. By analysing
radial velocity profiles and by fitting a kinematic model of the observed
velocity field, we confirm the literature result that NGC 4656 consists of one
single body instead of two objects. We estimated a dynamical mass of
$6.8^{1.8}_{-0.6}\times10^{9}$ M$_{\odot}$ and R of 12.1 kpc from the kinematic
model of NGC 4656. Although the observed velocity field is dominated by
rotation at large scales (V$_{max}$/$\sigma\gtrsim$2.8), important
non-rotational motions are present at small scales. Based on these new results,
and on previously published information, we propose that NGC 4656 and 4656UV
are a pair of interacting galaxies. NGC 4656UV is a companion of NGC 4656 and
it does not have a tidal origin. The interaction between the two could have
triggered the star formation in NGC 4656UV and increased the star formation in
the northeast side of NGC 4656.
