Complex molecular gas kinematics in the inner 5 kpc of 4C12.50 as seen
  by ALMA
  The nearby system 4C12.50, also known as IRAS 13451+1217 and PKS 1345+12, is
a merger of gas-rich galaxies with infrared and radio activity. It has a
perturbed interstellar medium (ISM) and a dense configuration of gas and dust
around the nucleus. The radio emission at small ($\sim$100 pc) and large
($\sim$100 kpc) scales, as well as the large X-ray cavity in which the system
is embedded, are indicative of a jet that could have affected the ISM. We
carried out observations of the CO(1-0), (3-2), and (4-3) lines with the
Atacama Large Millimeter Array (ALMA) to determine basic properties (i.e.,
extent, mass, and excitation) of the cold molecular gas in this system,
including its already-known wind. The CO emission reveals the presence of
gaseous streams related to the merger, which result in a small
($\sim$4kpc-wide) disk around the western nucleus. The disk reaches a
rotational velocity of 200 $kms^{-1}$ , and has a mass of
3.8($\pm$0.4)$\times$10${^9}M_{\odot}$. It is truncated at a gaseous ridge
north of the nucleus that is bright in [O III]. Regions with high-velocity CO
emission are seen at signal-to-noise ratios of between 3 and 5 along filaments
that radially extend from the nucleus to the ridge and that are bright in [O
III] and stellar emission. A tentative wind detection is also reported in the
nucleus and in the disk. The molecular gas speed could be as high as 2200
$kms^{-1}$ and the total wind mass could be as high as
1.5($\pm$0.1)$\times$10$^9M_{\odot}$. Energetically, it is possible that the
jet, assisted by the radiation pressure of the active nucleus or the stars,
accelerated clouds inside an expanding bubble.
