The Minnesota Automated Plate Scanner
North Galactic Pole (MAPS-NGP) Survey
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 zero-pointed 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.
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 of the above image of the MAP-NGP Catalog is available online ( 1.86MB ).