We present high-resolution ( \sim 2.5″ ) observations of ^ { 12 } CO J =6-5Â towards the luminous infrared galaxy VV 114 using the Submillimeter Array .
We detect ^ { 12 } CO J =6-5Â emission from the eastern nucleus of VV 114 but do not detect the western nucleus or the central region .
We combine the new ^ { 12 } CO J =6-5Â observations with previously published or archival low- J CO observations , that include ^ { 13 } CO J =1-0Â 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 _ { { { } ^ { 12 } CO } } ) of the molecular gas .
We find that the most probable scenario for the eastern nucleus is a cold ( T _ { kin } Â = 38 K ) , moderately dense ( n _ { { H _ { 2 } } } Â = 10 ^ { 2.89 } cm ^ { -3 } ) molecular gas component .
We find the most probable ^ { 12 } CO to ^ { 13 } CO abundance ratio ( [ ^ { 12 } CO ] / [ ^ { 13 } CO ] ) is 229 , roughly three times higher than the Milky Way value .
This high abundance ratio may explain the observed high ^ { 12 } CO/ ^ { 13 } CO line ratio ( > 25 ) .
The unusual ^ { 13 } CO J =2-1/ J =1-0 line ratio of 0.6 is produced by a combination of moderate ^ { 13 } CO optical depths ( \tau = 0.4 - 1.1 ) and extremely subthermal excitation temperatures .
We measure the CO-to-H _ { 2 } conversion factor , \alpha _ { CO } to be 0.5 ^ { +0.6 } _ { -0.3 } M _ { \odot } ( K km s ^ { -1 } pc ^ { 2 } ) ^ { -1 } , which agrees with the widely used factor for ultra luminous infrared galaxies of Downes \& Solomon ( 1998 ; \alpha _ { CO } =0.8 M _ { \odot } ( K km s ^ { -1 } pc ^ { 2 } ) ^ { -1 } ) .