Detection of a Corrugated Velocity Pattern in the Spiral Galaxy NGC 5427

Alfaro, E. J., Pérez, E., González Delgado, R. M., Martos, M. A., and Franco, J.
The Astrophysical Journal, Volume 550, Issue 1, pp. 253-260.


Here we report the detection, in Hα emission, of a radial corrugation in the velocity field of the spiral galaxy NGC 5427. The central velocity of the Hα line displays coherent, wavy-like variations in the vicinity of the spiral arms. The spectra along three different arm segments show that the maximum amplitude of the sinusoidal line variations are displaced some 500 pc from the central part of the spiral arms. The peak blueshifted velocities appear some 500 pc upstream of the arm, whereas the peak redshifted velocities are located some 500 pc downstream of the arm. This kinematical behavior is similar to the one expected in a galactic bore generated by the interaction of a spiral density wave with a thick gaseous disk, as recently modeled by Martos & Cox. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias.