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 Surveys. An attempt was made to classify arm strengths and a search for nearby neighbor galaxies was conducted. In a statistical analysis of the data gathered in this survey it was determined that among 75 galaxies with well classified asymmetric arms, only four were found to have no nearby neighbor within a separation of 5 log D25. The classification of these four systems as Magellanic type galaxies is highly questionable [Corwin, private communication (1989)]. In no case was a bright, dominant arm classified in a system in which a clear neighbor galaxy was absent. The frequency distribution of apparent separations, which is strongly peaked at small separations, suggests that the observed galaxy pairs are not due to chance optical alignments, but are in fact the result of physical associations. Hence, scenarios invoking the formation of offset bars and/or dominant spiral arms through some tidal interaction mechanism might be attractive, since a common trait among the Magellanic spirals appears to be the presence of a physical neighbor.