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G. Byrd (University of Alabama, Tuscaloosa, U.S.A.), M. Valtonen (Tuorla Observatory, Turku University, Finland)
Proposed nuclear activity mechanisms in disk galaxies range from internal bars to external tidal perturbation by companions. In a previous simulation survey, we estimated the tidal perturbation necessary to induce nuclear activity in disk galaxies. We compare the simulation and simple dynamical time scale expectations to Markarian activity in SS Hubble type pairs in Karachentsev's list of double galaxies. These tidal expectations are seen in the SS doubles: An excess number of pairs where both are active over pairs with one active. An exclusion of activity from pairs where members are unequal in size compared to equal sized pair members. A smaller velocity difference between members of pairs with active members than between members of ``both normal" pairs. A smaller average size for pair members where both are active than for ``both normal" pairs. The simulations indicate that the necessary strength of tidal perturbation to induce activity is larger the more important the galaxy's inert halo is relative to the disk. We use these results with the survey by Holmerg of companions of disk galaxies to estimate the fraction of the spirals which should be currently active. We compare this fraction to that observed to estimate the importance of the halo relative to the disk of these spirals.
This work was support by the Academy of Finland.
The author(s) of this abstract have provided an email address for comments about the abstract: byrd@possum.astr.ua.edu