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Many interacting doubles and galaxies with interacting companions,
(Category 1 and 2)
show tails and loops, presumably because of the
interaction. But here is a class of galaxies which shows these tails
or loops where the galaxies appear to be single. This is an important
category because, if the galaxies really are single, it implies
internal activity is responsible. Perhaps jets that fall back, or
drift, or are perturbed by other objects in the vicinity, could give
rise to these observed forms. This is the reason, aside from the
morphological similarity, why the present Category should be
considered along with
Category 7: Galaxies with Jets.
Of course there is always the possibility that what looks like a
single galaxy may be something else: the central ``galaxy'' may be the
product of a past merger of two galaxies with the loops and tails
being the long-lived echos of the collision. Only detailed
investigation in each case, however, would be capable of establishing
this. If the galaxy is not obviously double and has luminous filaments
which are not straight, it is put into the present Category.
On the first page the object AM 2217-245 (= NGC 7252) is the
well-known ``Four Petal Daisy'' named by W.W. Morgan. Schweizer (1980)
has interpreted this as due to gravitational interaction of
companions; others would argue that it is a case of multiple ejection.
The pages following show an object AM 0031-565 on a photograph taken
with the Las Campanas 2.5m telescope. The SRC Schmidt Survey plate
shows that the main galaxy has a filamentary connection (showing dust
features and an interior condensation) out to the very faint nebula to
the south-west.
On page 15.9, the object AM 2258-595, known as the ``Flea'', is
illustrated. The stellar image on the end of the filament going
south-east is reported by Hawarden and Longmore to be blue and
featureless but by Arp to be a low redshift star (both private
communication).
CATEGORY 15:
GALAXIES WITH TAILS LOOPS OF MATERIAL OR DEBRIS