Several external catalogs are used for astrometric and photometric calibration of DR9. These catalogs are currently availble in the indicated directories at NERSC, although we will soon make them available to the wider public.
External catalogs are used for masking regions near foreground sources in DR9 (e.g. to construct MASKBITS on the bitmasks page). These catalogs are available in the indicated directories at NERSC and at the listed urls.
- First, we select all objects classified as GCl or PN from the OpenNGC catalog of NGC/IC objects. In most cases, we use the published central coordinates and a circular mask with a radius taken from the majax attribute of this catalog; however, we update the radii of 14 of these objects based on visual inspection using the values (in degrees) in the NGC-star-clusters-radii.csv file.
- Next, we supplement this catalog with a list of nine additional globular clusters and compact open clusters from a variety of sources from the literature. This supplemental catalog can be found in the star-clusters-supplemental.csv file.
- Finally, we add two Local Group galaxies to this catalog, Fornax and Sculptor. We include these objects in this catalog because the normal pipeline led to the detection of tens of millions of additional sources which proved problematic to photometer. Consequently, in the part of the sky occupied by these galaxies DR9 only contains photometry for Gaia point sources.
The final input catalog was built using the build-cluster-catalog.py script and can be found in the legacypipe software product or at the publicly-accessible directory given above. Objects in this mask are given the CLUSTER bit on the bitmasks page.