Galaxies do not exist in total isolation. They interact with their
environment and they modify their surroundings through nuclear
activity, galactic winds, tidal encounters and collisions. While this
activity is not necessarily a continuous phenomenon, its effect on the
dynamics and long-term evolution of galaxies and galactic systems is
undoubtedly significant. Galaxies are the cumulative result of both
quiescent and catastrophic evolution. It is the purpose of this
Catalogue to highlight the most spectacular phases of galactic
evolution, and perhaps formation, by drawing attention to the basic
forms in which this activity is manifest.
In addition to cataloguing individual galaxies, the identification
and study of associations is important. The relatively recent advent
of wide-field, fast Schmidt telescopes has enabled the earlier
emphasis on individual galaxies to be shifted to such
associations. For example, at the turn of the century Keeler
(1900,
1908),
Curtis (1918),
Pease (1917,
1920)
and others published
many remarkable large-scale prints of individual galaxies, as
photographed by the small-field reflectors of the time. This
individual approach to galaxies culminated in the production of
atlases such as
Evans' (1957)
Cape Photographic Atlas of Southern Galaxies,
Sersic's (1968)
Atlas de Galaxies Australes,
Sandage's (1961)
Hubble Atlas of Galaxies and
Sandage and Tammann's
(1981)
Revised Shapley-Ames Catalogue which were basically illustrative of
classification systems based on symmetry, and focussed on single
galaxies in isolation.
The Schmidt telescopes have therefore provided a new perspective,
unavailable to earlier generations of extragalactic
astronomers. Pairs, triples and clusters of galaxies became
immediately apparent to the casual observer, whereas previously any
associations had to be hunted laboriously out of catalogues and
listings of uncertain completeness and/or reliability. The wide-field
Schmidt also made it possible to survey the whole sky. A complete
census of any given kind of object could be made and a statistical
analysis could then be performed.
The Palomar Observatory Sky Survey, made with the 48-inch Schmidt,
resulted in new galaxy and cluster searches being undertaken. For
instance Abell (1958)
catalogued and classified the relatively
conspicuous clusters of galaxies, while Zwicky and his collaborators
(Zwicky, Herzog and
Wild 1960;
Zwicky and Herzog 1963,
1966,
1968;
Zwicky, Karpowicz and
Kowal 1965;
Zwicky and Kowal 1968)
identified
all galaxies down to mpg 15.5 mag, while also noting pairs, triples,
etc. and outlining clusters.
Another of the outstanding contributions of the Schmidt telescope
has been to locate among myriad galaxies just those that are
spectacularly peculiar. The study of these objects has helped us
understand some physical processes and at the same time confronts us
with many more that we do not understand. Working from Sky Survey
paper prints
Vorontsov-Velyaminov
(1959)
produced an
Atlas and Catalogue of Interacting
Galaxies which was soon followed by
Arp's (1966)
Atlas of Peculiar Galaxies.
While many of these objects were
followed up and studied with large-aperture reflectors their
relationship to neighbouring galaxies required the wide-field
perspective afforded by the Schmidt telescopes.
Photography to slightly fainter surface-brightness levels than usual
can often reveal the much larger outer areas of many galaxies. In turn
these outer regions, being less dense, can reveal perturbations and
distortions more easily. These perturbations can come from internal
activity such as explosions or ejections, or from interaction with
neighbouring objects. Naturally this means that the regions
surrounding galaxies must be carefully studied. It is the combination
of fainter surface-brightness detection and wide-field registration
that enabled this new area of astronomical research to be opened up.
The introduction by Kodak of their fine-grained IIIa-J emulsion has
made it practical to discover and study these faint features in a
systematic way. So in combining the wide-field surveying capabilities
of the Schmidt telescope and the deeply penetrating exposures of the
IIIa-J emulsion, the SRC Southern Sky Survey has provided a unique
source of data on peculiar galaxies and associations. We have used
this source material to produce what we hope is a complete and
detailed catalogue of all the most interesting galaxies and most
striking apparent associations of galaxies in the southern sky.
INTRODUCTION AND OVERVIEW