Click for previews of the images in this category.

Click for the ASCII format of this category.

In the Atlas of Peculiar Galaxies (Arp 1966) this Category was called ``companions attached to spiral arms''. It was one of the best-defined and important categories and was ordered according to the relative size of the companion, going from the smallest to largest. In the present Catalogue it is clear that there are four parameters which could characterize an M51-type: (1) relative size of companion, (2) openness of spiral arm on which the companion appears, (3) type of central spiral, and (4) type of companion galaxy.

Any of these parameters, or others, might be deemed the most significant by which to order the Category. In the illustrations we have arranged the objects very approximately by the degree of openness of the arm with which the companion seems to be associated.

The first object illustrated, AM 0021-623, is considered to be a prototype object of this Category. The picture shown is from a 4m CTIO plate (1413A). On page 9.4, object AM 1823-513 is an M51-type in a chain of galaxies and is a reminder that there are some additional examples of M51-types in Category 17. On the same page, object AM 2025-224 appears to be of a type discussed by Vorontsov-Velyaminov (1976, 1977) where there is a companion on the end of each arm. The object is small, however, and requires better resolution in order to check this conclusion. On page 9.8, AM 1950-585 exhibits an apparent companion which is an M51-type and is also illustrated under Category 8. On the same page, object AM 0324-524 has two galaxies south of the obvious spiral, connected by a very faint filament to the other. On page 9.9 the picture shown is from a plate taken with the 2.5m Las Campanas telescope (CD 591) in about one arc second seeing. Immediately following, page 9.10 contains another picture taken with the same telescope (CD 587). On page 9.11 a 4m CTIO photograph is shown (1377A).