The first eleven maps show the location of 2367 galaxies as they lie on the sky. These are the galaxies that were known to have velocities less than 3,000 kilometers/ second at the time the cartography of the maps began.
The only aspect of these maps that requires significant explanation is the coordinate system. Galactic coordinates are used. The equator in this system is the plane of the Milky Way Galaxy. The zero point in longitude is the Galactic Center. In the equator of the Milky Way, there are numerous clouds of interstellar dust that obscure our view of objects, in addition to a great enhancement in the density of stars. Consequently, our clear windows onto the Universe beyond the Milky Way are away from the Galactic equatorial regions and toward the poles.
The entire sky is shown on 10 plates. A hemisphere is displayed on a polar map that highlights the region poleward of 60 degrees and four mid-latitude maps that highlight the latitude range 0 to 60 degrees in longitude intervals of 90 degrees.
The zone of obscuration associated with the equator of the Milky Way Galaxy is indicated by the darkened background on these maps. Of course, there is not an abrupt transition from transparency to opacity. At the transitional contour that is plotted, roughly 40 percent of the blue light of a distant galaxy has been absorbed by the intervening dust. Some galaxies have been detected through considerable amounts of dust. Generally, there is not too much bias against the detection of galaxies that are farther than 30 degrees from the Galactic Equator, but extreme bias against those within 20 degrees of the Equator.
Aside from the problem of Galactic obscuration there is reasonably good all-sky coverage with the present sample of 2367 galaxies. Unpublished material obtained with the Parkes Radio Telescope in Australia is included, with the consequence that there is reasonable homogeneity between the northern and southern celestial hemispheres.
A symbol is plotted at the Galactic latitude and longitude of each galaxy in the sample. The symbol denotes the morphological type of the galaxy. The size of the symbol is a measure of the angular size of the galaxy as we see it, so nearer galaxies tend to be bigger than more distant galaxies. The color of the symbol is coded to the systemic velocity of the galaxy. Nearby galaxies with small velocities, or redshift, are represented by cool, blue colors and more distant galaxies with larger redshift are represented by warm, red colors. The specifics of these details are described in the legends on each plate.
There are enlargements of the two most crowded regions: The Fornax Cluster on Plate 8, and the Virgo Cluster on Plate 11.
Further information on the 2367 galaxies that constitute our sample are provided in the companion publication, the Nearby Galaxies Catalog (ref. 1).
Enough of words. The maps are more eloquent.
* More extensive discussion is reserved for articles that will be submitted to technical journals in due course.