IAU Symposium Abstract S186-040T


The Counterrotating Phenomenon through the Hubble Sequence


F. Prada1
1 Instituto de Astrof'\i sica de Canarias < fprada@iac.es >



There is an increasing observational evidence of the presence of retrograde motions in ellipticals and early type spiral galaxies. However, little is known about this phenomenon in barred and late ordinary spirals. Here, we present the current status of an on-going research programme at the Observatorio del Roque de los Muchachos (La Palma) to establish the presence and nature of the counterrotating phenomenon across the Hubble sequence. We report the discovery of a warm counterrotating component in the central regions of the late spiral NGC~7331 and the barred NGC~5728 galaxies. The stellar line-of-sight velocity distribution was determined using near-IR long-slit spectroscopy of the calcium triplet absorption feature with the William Herschel Telescope. In NGC~7331 we find the first case of a counterrotating bulge, while in NGC~5728 a central counterrotating component was discovered in a barred galaxy. These results show that retrograde motion extends throughout the Hubble sequence. The implications of this in the context of the theories of galaxy formation are discussed.