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This interesting Category contains groups of four or more galaxies
which stand out in brightness and closeness as a group, and which are,
at the same time, noticeably aligned. The frequency of this occurrence
in the full Catalogue is reflected in the large number of
illustrations we present. One interesting aspect of these chains is
that many contain disturbed or peculiar galaxies. Aside from the
possible physical significance of this feature, it can be used to
support the physical reality of the chains since it is much less
likely that peculiar galaxies could be unrelated inter-lopers from the
field.
The chaining tendency which we investigate here is also apparently
connected with the tendency for the Interacting Triplets through
Quintets (Categories 3 through
5) to be aligned and the tendency for
apparent companions of larger galaxies
(Category 8) to be aligned
diametrically.
The scheme for presenting this Category is to give the most striking
alignments first. The first three pages show well aligned chains of
peculiar, disturbed galaxies. On page 17.4 the object AM 2315-423
could be classed as a disturbed spiral with diametric companions. The
succeeding pages show fairly straight alignments of varying galaxy
composition. On page 17.9 the chains start to have some curvature to
them. From page 17.9 through 17.18 chains are illustrated that show
both increasing apparent curvature and increasing thickness of the
linear structure. On page 17.12 some of the galaxies which make up the
object AM 1241-402 were first discussed by
Sersic (1974), and have
recently been investigated by Lausten and West (1980). The object AM
0218-321 (page 17.15) was also illustrated in
Category 4: Interacting Quartets. On page
17.18 there are some examples of small chains that
appear to be more distant. By the end of this Category, the chains
which are illustrated (page 17.24) are either very loose, or have
nearby apparent members which are not aligned, thus providing a
transition to Category 18: Groups.
CATEGORY 17:
CHAINS