NUGA PdBI ¹²CO(1–0) contours are overlaid onto the gravitational torque map computed from the HST-NICMOS F160W image (t(x,y)  ×  Σ(x,y), as defined in text) in the center of NGC 3627. The map is deprojected, and rotated so that the major axis of the galaxy is oriented parallel to the abscissa Ox. The continuum line is oriented along the large-scale bar in the plane of the galaxy (PA = 35°), the dashed one orthogonally to the continuum line. The quadrants labeled with (+) refer to positive torques, while those labeled with ( − ) to negative torques. The derived torques change sign as expected in a butterfly diagram.