Millimeter ( CO ) observations of 5 double-nucleus ultraluminous infrared galaxy ( ULIG ) mergers are presented .
With nuclear separations of 3 - 5 kpc , these galaxies are in the “ intermediate ” stages of the merger process .
A preliminary comparison of the distribution of molecular gas ( the likely fuel source for both starbursts and active galactic nuclei : AGN ) shows a tendency for molecular gas to be associated with the AGN nucleus of ULIGs with “ warm ” , Seyfert-like infrared colors ( f _ { 25 \mu { m } } / f _ { 60 \mu { m } } \geq 0.20 ) and associated with both stellar nuclei of ULIGs with “ cool ” infrared colors ( f _ { 25 \mu { m } } / f _ { 60 \mu { m } } < 0.2 ) .
Studies of ULIGs with a wide range of nuclear separations using the high resolution and increased sensitivity of ALMA will provide a larger statistical sample with which the gas distribution , molecular gas masses , and densities can be determined as a function of the evolutionary stage , starburst and AGN activity , and lookback time .