randoms-seed-pixnum

Summary:

DESI inside-the-footprint random catalogs contain a single binary table covering the entire Legacy Surveys footprint. They contain meta information (the number of observations, the depth, etc.) derived from pixels in Legacy Surveys CCDs at random RA/Dec coordinates.

Naming Convention:

randoms-seed-iteration-hp-pixnum.fits, where seed represents the random seed used to generate the catalog, iteration lists the iteration number of the catalog (several iterations are typically conducted during a given run to generate random catalogs), and pixnum is the HEALPixel number.

Regex:

randoms-[0-9]+-hp-[0-9]+\.fits

File Type:

FITS, 14 GB

These files contain the same data as a standard “randoms” file, but split by HEALPixel, using the NSIDE=8, NESTED scheme. For example, given a standard randoms file, randoms-1-15.fits, randoms-1-15/randoms-1-hp-123.fits would contain the portion of the data that is in pixel number 123.

These files have an additional header keyword in HDU1, e.g.

INFILE  = '/global/cfs/cdirs/desi/target/catalogs/dr9/0.49.0/randoms/resolve/randoms-1-17.fits'

which is the original randoms file prior to splitting by HEALPixel.

See the standard randoms file description.