Hα kinematics of S⁴G spiral galaxies - I. NGC 864

We present a study of the kinematics of the isolated spiral galaxy NGC864, using Ha Fabry- Perot data obtained with the Galaxy Ha Fabry-Perot System (GHaFaS) instrument at the William Herschel Telescope in La Palma, complemented with images at 3.6 μm, in the R band and in Ha filter, and integral-field spectroscopic data. The resulting data cubes and velocity maps allow the study of the kinematics of the galaxy, including in-depth investigations of the rotation curve, velocity moment maps, velocity residual maps, gradient maps and position- velocity diagrams. We find asymmetries in the velocity field in the bar zone, caused by non-circular motions, probably in response to the potential of the bar. We also find a flatprofile bar, in agreement with the strong bar, with the grand design spiral pattern, and withthe gap between the ends of the bar and the start of the spiral arms. We quantify the rate of massive star formation, which is concentrated in the twospiral arms.