SEYFERT-GALAXIES WITH COMPANIONS - ORBITAL AND KINEMATIC CLUES TO AGNTRIGGERING

This paper presents imaging and optical spectroscopy of paired Seyfert galaxies and their companions. The aim is to seek common properties o f Seyfert galaxies in interacting systems, which might provide evidenc e of AGN triggering in a way independent of the usual two-sample stati stics which have proven ambiguous on this issue. Three kinds of compar ison have been made-the kinds of interactions involving Seyfert galaxi es, the relative luminosities of the Seyferts and their companions, an d the level of kinematic disturbance as measured from rotation curves. (1) Dynamics and tidal features have been used to determine (or at le ast limit) the sense of orbital motion (direct/retrograde/polar with r espect to the Seyfert galaxy's disk) for many of these pairs. There is no obviously preferred kind of interaction-direct, polar, and retrogr ade encounters are all well represented, despite the gross differences in dynamical response of a disk to these various kinds of encounter. To the extent that triggering of Seyfert nuclei occurs due to tidal en counters, the existence of a perturbation seems more important than it s exact duration or detailed effects on the disk. However, the ratio o f merging to paired Seyferts is higher than for disk galaxies in gener al, consistent with more effective triggering of AGN in this specific phase; the implied time scale for enhanced occurrence during mergers i s the same as the timescape for merger remnants to appear as such, a f ew disk-edge crossing times (typically several times 10(8) yr). (2) Se yfert nuclei occur preferentially in the brighter members of galaxy pa irs, by a median of 0.93 mag after making the maximal correction for c ontaminating nonstellar light in the nuclei. Only about 1/3 of this ef fect can be accounted for by the known tendency of Seyfert nuclei to o ccur in more luminous galaxies. Enhancement of AGN by interactions is evidently more effective for more luminous galaxies (though this will also be the case if both star formation and AGN occurrence are enhance d in the same galaxies). (3) The rotation curves of the paired Seyfert s show systematically small regions of rising or solid-body rotation c ompared to the disk radius, as a group comparable to Sa but very diffe rent from Sb or Sc galaxies (even for Seyfert galaxies with Hubble typ e later than Sa). There is weak evidence that this difference is also present with respect to more isolated Seyfert galaxies. Despite the ob vious utility of a dynamically disturbed disk for transport of angular momentum and ''feeding the monster,'' Seyfert galaxies in pairs actua lly have smaller kinematic disturbances (measured by the maximum depar ture from a symmetric rotation curve, normalized to the full rotation amplitude) than found in a complete sample of non-Seyfert spirals in p airs. (C) 1996 American Astronomical Society.