Cold Molecular Gas in Merger Remnants: I. Formation of Molecular Gas
  Disks
  We present < 1 kpc resolution CO imaging study of 37 optically-selected local
merger remnants using new and archival interferometric maps obtained with ALMA,
CARMA, SMA and PdBI. We supplement a sub-sample with single-dish measurements
obtained at the NRO 45 m telescope for estimating the molecular gas mass (10^7
- 10^11 M_sun), and evaluating the missing flux of the interferometric
measurements. Among the sources with robust CO detections, we find that 80 %
(24/30) of the sample show kinematical signatures of rotating molecular gas
disks (including nuclear rings) in their velocity fields, and the sizes of
these disks vary significantly from 1.1 kpc to 9.3 kpc. The size of the
molecular gas disks in 54 % of the sources is more compact than the K-band
effective radius. These small gas disks may have formed from a past gas inflow
that was triggered by a dynamical instability during a potential merging event.
On the other hand, the rest (46 %) of the sources have gas disks which are
extended relative to the stellar component, possibly forming a late-type galaxy
with a central stellar bulge. Our new compilation of observational data
suggests that nuclear and extended molecular gas disks are common in the final
stages of mergers. This finding is consistent with recent major-merger
simulations of gas rich progenitor disks. Finally, we suggest that some of the
rotation-supported turbulent disks observed at high redshifts may result from
galaxies that have experienced a recent major merger.
