Rotation of the bulge components of disk galaxies

In order to investigate dynamical differences between bulges and elliptical galaxies, absorption-line velocities and velocity dispersions were measured along several slit positions in the bulge components of four edge-on S0-Sb galaxies. The present bulges rotate more rapidly than bright ellipticals. Their kinematic properties are strikingly uniform and, in many cases, are well described by dynamical models of rotationally flattened oblate spheroids with isotropic residual velocities. Given that the disk potential also contributes to the flattening, little or no anisotropy is required to explain the shapes of bulges. The observation that bulges rotate rapidly suggests that they were formed by a dissipational process. In general, the detailed behavior of the two-dimensional velocity fields is consistent with classical dissipational collapse theories of galaxy formation. Rotation, dispersion, and line strength data for the sample galaxies are given.