Kinematic properties of gas and stars in 20 disc galaxies

Ionized gas and stellar kinematical parameters have been measured along the major axis of 20 nearby disc galaxies. We discuss the properties of each sample galaxy, distinguishing between those characterized by regular or peculiar kinematics. In early-type disc galaxies, ionized gas tends to rotate faster than stars and to have a lower velocity dispersion (V_g > V_star and sigma_g < sigma_star), whereas in late-type spirals, gas and stars show almost the same rotation velocities and velocity dispersions (V_g =~ V_star and sigma_g =~ sigma_star ). Incorporating the early-type disc galaxies studied by Bertola et al. (1995), Fisher (1997) and Corsini et al. (1999), we have compiled a sample of some 40 galaxies for which the major-axis radial profiles of both the stellar and gaseous components have been measured. The value of sigma_star measured at R_e/4 turns out to be strongly correlated with the galaxy morphological type, while sigma_g is not and sometimes takes values above the range expected from thermal motions or small-scale turbulence.