The MAPS-NGP Catalog is a diameter-limited catalog of all galaxies
greater than 10 arcseconds in diameter on Palomar Sky Survey (Epoch I) plates
within 30 degrees of the North Galactic Pole. While there are typically plate-to-plate
variations in the limiting surfact brightness of this survey, the mean surface
brightness limit is near 23.5 magnitudes per square arcseconds (with a sigma
of about 1 magnitude per square arcsecond).

This is a plot of the 211,733 galaxies in the Minnesota Automated Plate Scanner North Galactic
Pole (MAPS-NGP) catalog which don't have any known image defects (that is
they are not flagged). This plot contains all the galaxies larger than 10
arcseconds in angular diameter over the twelfth of the sky closest to the
north galactic pole (the point in the sky straight out of the plane of the Milky
Way Galaxy). For a sense of scale, the moon is roughly 1800 arcseconds in angular
diameter, so this is every galaxy down to those about 1/200 the diameter of
the moon in the sky. The galaxies are all represented by dots where the dot
size depends on the actual angular diameter of the galaxy. The dot color depends
on the plate-based O-E color of the galaxy (colors have been zeropointed on
a plate-by-plate basis). The group of large dots near the center of this plot
is the Coma Supercluster, about 100 Megaparsecs (about 326 million light
years) away. The larger group of large galaxies near 12h30m in Right Ascension
and 12 degrees Declination is the Virgo Cluster, the center of which
is about of which is about 15 Megaparsecs (about 50 million light years) away.
We actually reside on the edge of this cluster and the reason it appears so
large on the sky is that it is to close. The other large galaxies in this plot
tend to show the nearby structure of the universe, with the tiny galaxies generally
being very far away. The circular areas without any galaxies are regions around
SAO stars or plate defects which have been deleted from the catalog.
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The entire MAPS-NGP catalog can be downloaded in gzipped gzipped
ASCII format (
40MB
). If you plan to use the catalog, please be sure to read the MAPS-NGP
catalog README (
11KB
) first, as it describes the catalog and its contents. Details on the construction
of the MAPS-NGP can be found in Chapter
5 of my
Ph.D. Thesis. A full-resolution PDF version (requires Adobe Acrobat to view)
of the above image of the MAP-NGP Catalog is available
online (
1.86MB
).
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