Active Galactic Nucleus and Extended Starbursts in a Mid-stage Merger
  VV114
  High resolution (0.4 arcsec) Atacama Large Millimeter/submillimeter Array
(ALMA) Cycle 0 observations of HCO+(4-3) and HCN(4-3) toward a mid-stage
infrared bright merger VV114 have revealed compact nuclear (<200 pc) and
extended (3 - 4 kpc) dense gas distribution across the eastern part of the
galaxy pair. We find a significant enhancement of HCN(4-3) emission in an
unresolved compact and broad (290km/s) component found in the eastern nucleus
of VV114, and we suggest dense gas associated with the surrounding material
around an Active Galactic Nucleus (AGN), with a mass upper limit of < 4 x 10^8
Msun. The extended dense gas is distributed along a filamentary structure with
resolved dense gas concentrations (230pc; 10^6 Msun) separated by a mean
projected distance of 600 pc, many of which are generally consistent with the
location of star formation traced in Pa alpha emission. Radiative transfer
calculations suggest moderately dense (10^5 - 10^6 cm^-3) gas averaged over the
entire emission region. These new ALMA observations demonstrate the strength of
the dense gas tracers in identifying both the AGN and star formation activity
in a galaxy merger, even in the most dust enshrouded environments in the local
universe.
