2014ApJ...796L..15S

We present high-resolution archival Atacama Large Millimeter/submillimeter Array (ALMA) ¹²CO J = 3-2 and J = 6-5 and HCO⁺ J = 4-3 observations and new CARMA ¹²CO and ¹³CO J = 1-0 observations of the luminous infrared galaxy NGC 1614. The high-resolution maps show the previously identified ring-like structure while the ¹²CO J = 3-2 map shows extended emission that traces the extended dusty features. We combined these new observations with previously published Submillimeter Array ¹²CO and ¹³CO J = 2-1 observations to constrain the physical conditions of the molecular gas at a resolution of 230 pc using a radiative transfer code and a Bayesian likelihood analysis. At several positions around the central ring-like structure, the molecular gas is cold (20-40 K) and dense (>10^3.0/cm3). The only region that shows evidence of a second molecular gas component is the "hole" in the ring. The ¹²CO-to-¹³CO abundance ratio is found to be greater than 130, more than twice the local interstellar medium value. We also measure the CO-to-H₂ conversion factor, α_CO, to range from 0.9 to 1.5 M_☉(K km/s pc²)^–1.