Twin peaks of CO emission in the central regions of barred galaxies

New high-resolution (∼2″) CO maps of the central regions of three barred galaxies show that the strongest CO emission arises from twin peaks, which are oriented perpendicular to the large-scale stellar bars and located where dust lanes intersect nuclear rings of H II regions. These twin gas concentrations can be explained by the crowding of gas streamlines near inner Lindblad resonances. In a fourth barred system, the nuclear starburst galaxy NGC 3504, a large concentration of molecular gas is centered on the nucleus, apparently inside an inner Lindblad resonance. Strong tidal forces in and beyond the ILR can disrupt the clouds there, and this may account for the fact that the starburst is limited to smaller radii.