Top: map of the gravitational torque, (t(x,y) × Σ(x,y), as defined in text) in the center of NGC 1566. The torques change sign as expected in a four-quadrant pattern (or butterfly diagram). The orientation of the quadrants follows the nuclear bar’s orientation. In this deprojected picture, the major axis of the galaxy is oriented parallel to the horizontal axis. The inclined line reproduces the mean orientation of the bar (PA = 40° on the deprojected image). Bottom: deprojected image of the CO(3–2) emission, at the same scale, and with the same orientation, for comparison. The axes are labeled in arcsecond relative to the center. The color scales are linear, in arbitrary units.