Resolved CO (1 -> 0) nuclei in IRAS 14348-1447: Evidence for massive bulgeprogenitors to ultraluminous infrared galaxies

High-resolution, CO (1 --> 0) interferometry of the ultraluminous infrared galaxy IRAS 14348-1447 is presented. The merger system has a molecular gas mass of similar to 3 x 10(10) M., and a projected nuclear separation of 4.8 kpc (3."5), making it one of the most molecular gas-rich galaxies known an d an ideal candidate for studying the intermediate stages of an ultralumino us merger event. The CO morphology shows two molecular gas components assoc iated with the stellar nuclei of the progenitors, consistent with the idea that the molecular disks are gravitationally bound by the dense bulges of t he progenitor galaxies as the interaction proceeds. In contrast, less lumin ous infrared galaxies observed to date with projected nuclear separations o f less than or similar to 5 kpc show a dominant CO component between the st ellar nuclei. This discrepancy may be an indication that the progenitors of mergers with lower infrared luminosity do not possess massive bulges and t hat the gas is stripped during the initial encounter. A comparison of the C O and radio luminosities of the northeast and southwest components of IRAS 14348-1447 show them to have comparable radio and CO flux ratios off(NE)lf( SW)similar to 0.6, possibly indicating that the amount of star-forming mole cular gas in the progenitors is correlated with the supernovae rate. The es timate of molecular gas masses of the nuclei and the extent of the radio em ission are used to infer that the nuclei of IR 14348-1447 have gas densitie s comparable to the cores of elliptical galaxies.