Detection of a corrugated velocity pattern in the spiral galaxy NGC 5427

Here we report the detection, in H alpha emission, of a radial corrugation in the velocity field of the spiral galaxy NGC 5427. The central velocity o f the H alpha line displays coherent, wavy-like variations in the vicinity of the spiral arms. The spectra along three different arm segments show tha t the maximum amplitude of the sinusoidal line variations are displaced som e 500 pc from the central part of the spiral arms. The peak blueshifted vel ocities appear some 500 pc upstream of the arm, whereas the peak red-shifte d velocities are located some 500 pc downstream of the arm. This kinematica l behavior is similar to the one expected in a galactic bore generated by t he interaction of a spiral density wave with a thick gaseous disk, as recen tly modeled by Martos & Cox.