PROPERTIES OF THE MAGELLANIC TYPE SPIRALS .2. THE FREQUENCY OF COMPANION GALAXIES

A survey of the largest (log D25 > 1.3) Magellanic spiral galaxies in the RC3 catalog was performed using the Palomar and UK Schmidt Sky Sur veys. An attempt was made to classify arm strengths and a search for n earby neighbor galaxies was conducted. In a statistical analysis of th e data gathered in this survey it was determined that among 75 galaxie s with well classified asymmetric arms, only four were found to have n o nearby neighbor within a separation of 5 log D25. The classification of these four systems as Magellanic type galaxies is highly questiona ble [Corwin, private communication (1989)]. In no case was a bright, d ominant arm classified in a system in which a clear neighbor galaxy wa s absent. The frequency distribution of apparent separations, which is strongly peaked at small separations, suggests that the observed gala xy pairs are not due to chance optical alignments, but are in fact the result of physical associations. Hence, scenarios invoking the format ion of offset bars and/or dominant spiral arms through some tidal inte raction mechanism might be attractive, since a common trait among the Magellanic spirals appears to be the presence of a physical neighbor.