ALMA MULTI-LINE OBSERVATIONS OF THE IR-BRIGHT MERGER VV 114.

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 CH3OH 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−1), 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) × 107 (assuming a conversion factor of αCO = 0.8 ) at the tip of the southern tidal arm, as a potential site of tidal dwarf galaxy formation. [ABSTRACT FROM AUTHOR]