Aperture synthesis of CO emission in extremely luminous infrared galaxies

High-resolution aperture synthesis mapping of the CO (J = 1-0) emission has been carried out for the extremely luminous IRAS galaxies, VV 114, NGC 1614, VII Zw 31, and Mrk 231. For all of the galaxies except for VV 114, the observations show the existence of compact emission sources centered on the optical/IR nuclei. In VV 114, the observations reveal two concentrations of emission extending over an area of about 4 kpc. The mean molecular gas surface densities averaged over the compact regions of the galaxies reach 3000 solar masses/sq pc. It is suggested that the concentration of large masses of molecular gas in galactic nuclei initiates energetic activity in these galaxies via a nuclear starburst, possibly resulting in the formation of an active galactic nucleus. 14 refs