 |
|
|
|
|
Tri-color Imaging of Selected Arp Galaxies
By Tim Hunter
|
Abstract
Halton Arp published his Atlas of Peculiar Galaxies in 1966. It
is considered one of the definitive collections of anomalous
galaxies. His images were black and white photographs taken on
the Mount Palomar 200-inch telescope. Modern CCD technology now
makes it possible to take color CCD images of many of the Arp
galaxies using much smaller telescopes. The 24-inch f/5
telescope at the Grasslands Observatory was used to obtain
tri-color CCD images of a representative collection of 11 Arp
galaxies with a high quantum efficiency back-illuminated CCD
system combined with Johnson-Cousins R, V, B filters. These
galaxies are discussed in regard to galaxy color, galaxy
classification systems, and galaxy interactions. Most of the Arp
galaxies represent extreme examples of past and ongoing galaxy
interactions.
Introduction
In 1966 Halton Arp (1924- ) published his Atlas of Peculiar
Galaxies1. This work is now considered a classic in
the astronomical community. In the preface to his Atlas, Arp
states:
"The present Atlas specifically started from an attempt to
better understand spiral galaxies. Despite even recent analyses
from a contrary standpoint, I believe that gravitational orbits
in a stellar assemblage will not alone furnish satisfactory
explanations of galaxies. It is clear that the convolution which
spiral arms are seen to undergo in certain galaxies cannot be
performed by loci of stellar orbits. In the investigation of
these special spiral properties, therefore, galaxies which
showed unusual or perturbed arms or filamentary extensions were
sampled with high resolution photographs with the Palomar
200-inch telescope. Subjects were first drawn from the
pioneering work of Zwicky and Vorontsov-Velyaminov. So many
important objects emerged under high-resolution,
limiting-magnitude study, however, that the investigation into
the nature of spiral arms was temporarily postponed in order to
organize systematically these new phenomena into groups and
publish a representative sample of the best objects.” 1 |
|
|
NEXT |
|
Back to Top | Essay List |
|
