Spiral structure of the giant galaxy UGC 2885: Hα kinematics
The TAURUS I imaging Fabry-Perot spectrometer is used to map the velocity field of the giant spiral galaxy UGC 2885 in H-alpha emission at 5-arcsec resolution. Ripples in the velocity field around the minor axis indicate radial flows across the spiral arms. The radial flow speeds in the plane of the disk show 50-70 km/s peak-to-peak variation, suggesting that a strong density wave is present in the underlying stellar disk. Such high speeds may alternatively be a natural consequence of the open arm spiral patterns. Strong density waves may naturally occur in large spiral galaxies or in spiral galaxies as massive as UGC 2885.