Around the ring we go: The cold, dense ring of molecular gas in NGC 1614

Abstract

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 (>103.0 cm-3). 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, αCO, to range from 0.9 to 1.5 M⊙ (K km s-1 pc2)-1.