Resolved CO (1 --> 0) Nuclei in IRAS 14348-1447: Evidence for Massive Bulge Progenitors 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 approximately 3x1010 M middle dot in circle and a projected nuclear separation of 4.8 kpc (3&farcs;5), making it one of the most molecular gas-rich galaxies known and an ideal candidate for studying the intermediate stages of an ultraluminous merger event. The CO morphology shows two molecular gas components associated with the stellar nuclei of the progenitors, consistent with the idea that the molecular disks are gravitationally bound by the dense bulges of the progenitor galaxies as the interaction proceeds. In contrast, less luminous infrared galaxies observed to date with projected nuclear separations of less, similar5 kpc show a dominant CO component between the stellar nuclei. This discrepancy may be an indication that the progenitors of mergers with lower infrared luminosity do not possess massive bulges and that the gas is stripped during the initial encounter. A comparison of the CO and radio luminosities of the northeast and southwest components of IRAS 14348-1447 show them to have comparable radio and CO flux ratios of f&parl0;NE&parr0;&solm0;f&parl0;SW&parr0; approximately 0.6, possibly indicating that the amount of star-forming molecular gas in the progenitors is correlated with the supernovae rate. The estimate of molecular gas masses of the nuclei and the extent of the radio emission are used to infer that the nuclei of IR 14348-1447 have gas densities comparable to the cores of elliptical galaxies.
Evans
AS
Surace
JA
Mazzarella
JM