Luminous Infrared Galaxies with the Submillimeter Array. IV. 12CO J = 6-5 Observations of VV 114

We present high-resolution (~2.''5) observations of ¹²CO J = 6-5 toward the luminous infrared galaxy VV 114 using the Submillimeter Array. We detect ¹²CO J = 6-5 emission from the eastern nucleus of VV 114 but do not detect the western nucleus or the central region. We combine the new ¹²CO J = 6-5 observations with previously published or archival low-J CO observations, which include ¹³CO J = 1-0 Atacama Large Millimeter/submillimeter Array cycle 0 observations, to analyze the beam-averaged physical conditions of the molecular gas in the eastern nucleus. We use the radiative transfer code RADEX and a Bayesian likelihood code to constrain the temperature (T _kin), density (n_{H_{2}}), and column density (N_{^{12CO}}) of the molecular gas. We find that the most probable scenario for the eastern nucleus is a cold (T _kin = 38 K), moderately dense (n_{H_{2}} = 10^2.89 cm^-3) molecular gas component. We find that the most probable ¹²CO to ¹³CO abundance ratio ([¹²CO]/[¹³CO]) is 229, which is roughly three times higher than the Milky Way value. This high abundance ratio may explain the observed high ¹²CO/ ¹³CO line ratio (>25). The unusual ¹³CO J = 2-1/J = 1-0 line ratio of 0.6 is produced by a combination of moderate ¹³CO optical depths (τ = 0.4-1.1) and extremely subthermal excitation temperatures. We measure the CO-to-H₂ conversion factor, α_CO, to be 0.5^{+0.6}_{-0.3} M _⊙ (K km s^-1 pc²)^-1, which agrees with the widely used factor for ultra luminous infrared galaxies of Downes & Solomon (α_CO = 0.8 M _⊙ (K km s^-1 pc²)^-1).