2015ApJ...803...60S

We present Atacama Large Millimeter/submillimeter Array cycle 0 observations of the molecular gas and dust in the IR-bright mid-stage merger VV 114 obtained at 160-800 pc resolution. The main aim of this study is to investigate the distribution and kinematics of the cold/warm gas and to quantify the spatial variation of the excitation conditions across the two merging disks. The data contain 10 molecular lines, including the first detection of extranuclear CH₃ OH emission in interacting galaxies, as well as continuum emission. We map the ¹²CO(3-2)/¹²CO(1-0) and the ¹²CO(1-0)/¹³CO(1-0) line ratio at 800 pc resolution (in the units of K km/s), and find that these ratios vary from 0.2-0.8 and 5-50, respectively. Conversely, the 200 pc resolution HCN(4-3)/HCO⁺(4-3) line ratio shows low values (<0.5) at a filament across the disks except for the unresolved eastern nucleus which is three times higher (1.34±0.09). We conclude from our observations and a radiative transfer analysis that the molecular gas in the VV 114 system consists of five components with different physical and chemical conditions, i.e., (1) dust-enshrouded nuclear starbursts and/or active galactic nuclei, (2) widespread star-forming dense gas, (3) merger-induced shocked gas, (4) quiescent tenuous gas arms without star formation, and (5) H₂ gas mass of (3.8±0.7)x10⁷ M_☉ (assuming a conversion factor of α_CO= 0.8 M_☉) at the tip of the southern tidal arm, as a potential site of tidal dwarf galaxy formation.