============== randoms-allsky ============== :Summary: DESI allsky random catalogs contain a single binary table covering the entire sky. Inside the `Legacy Surveys`_ (LS) footprint they contain meta information (the number of observations, the depth, etc.) derived from pixels in Legacy Surveys CCDs at random RA/Dec coordinates. Outside the `LS`_ footprint they contain highly simplified columns. These files are a combination of the standard inside-the-footprint random catalogs and the simplified outside-the-footprint random catalogs. :Naming Convention: ``randoms-allsky-seed-iteration.fits``, where ``seed`` represents the random seed used to generate the catalog and ``iteration`` lists the iteration number of the catalog (several iterations are typically conducted during a given run to generate random catalogs). :Regex: ``randoms-allsky(-[0-9]+)?-[0-9]+\.fits`` :File Type: FITS, 12 GB Contents ======== ====== ======= ======== =================== Number EXTNAME Type Contents ====== ======= ======== =================== HDU0_ IMAGE Empty HDU1_ RANDOMS BINTABLE Random catalog table ====== ======= ======== =================== FITS Header Units ================= HDU0 ---- This HDU has no non-standard required keywords. Empty HDU. HDU1 ---- EXTNAME = RANDOMS Random catalog table Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ======== ============= ===== ======================================== KEY Example Value Type Comment ======== ============= ===== ======================================== NAXIS1 281 int Width of table in bytes NAXIS2 1124357626 int Number of rows in table FILENSID 2 int HEALPix nside covered by file FILENEST T bool HEALPix nested (not ring) ordering FILEHPX 11,5,4 str HEALPix pixel(s) covered by file DR 9 int `Legacy Surveys`_ (LS) Data Release used to generate randoms DENSITY 45000 int Number of random points generated per sq. deg. APRAD 0.75 float Aperture radius used to calculate flux-related quantities (arcsec) SEED 1 int Seed used to generate random catalog ADDMTL F bool ``True`` if MTL-related columns were added to the parent catalog used to build this catalog HPXNSIDE 64 int HEALPix nside HPXNEST T bool HEALPix nested (not ring) ordering SUPP F bool ``True`` if randoms were generated without using `LS`_ pixels RESOLVE T bool ``True`` if from unique imaging RESEED 626 int Seed used to re-shuffle combined random catalogs to ensure randomness MTLSPLIT T bool ``True`` if MTL-related columns were added to this random catalog ======== ============= ===== ======================================== Required Data Table Columns ~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. rst-class:: columns ============= ======== ============== =================== Name Type Units Description ============= ======== ============== =================== RA float64 deg Right ascension at pixel location DEC float64 deg Declination at pixel location BRICKNAME char[8] Name of the brick BRICKID int32 A unique Brick ID NOBS_G int16 Number of images at pixel location in `LS`_ g NOBS_R int16 Number of images at pixel location in `LS`_ r NOBS_Z int16 Number of images at pixel location in `LS`_ z PSFDEPTH_G float32 PSF-based depth at pixel location in `LS`_ g PSFDEPTH_R float32 PSF-based depth at pixel location in `LS`_ r PSFDEPTH_Z float32 PSF-based depth at pixel location in `LS`_ z GALDEPTH_G float32 Galaxy model-based depth at pixel location in `LS`_ g GALDEPTH_R float32 Galaxy model-based depth at pixel location in `LS`_ r GALDEPTH_Z float32 Galaxy model-based depth at pixel location in `LS`_ z PSFDEPTH_W1 float32 PSF-based depth in WISE W1 (AB mag system) PSFDEPTH_W2 float32 PSF-based depth in WISE W2 (AB mag system) PSFSIZE_G float32 arcsec Weighted average PSF FWHM in `LS`_ g PSFSIZE_R float32 arcsec Weighted average PSF FWHM in `LS`_ r PSFSIZE_Z float32 arcsec Weighted average PSF FWHM in `LS`_ z APFLUX_G float32 nanomaggy Total flux extracted in a 0.75 arcsec radius in g APFLUX_R float32 nanomaggy Total flux extracted in a 0.75 arcsec radius in r APFLUX_Z float32 nanomaggy Total flux extracted in a 0.75 arcsec radius in z APFLUX_IVAR_G float32 nanomaggy^-2 Inverse variance of APFLUX_G APFLUX_IVAR_R float32 nanomaggy^-2 Inverse variance of APFLUX_R APFLUX_IVAR_Z float32 nanomaggy^-2 Inverse variance of APFLUX_Z MASKBITS int16 Bit mask of possible problems with pixel (see the LS `DR9 bitmasks page`_) WISEMASK_W1 binary Bitwise mask for WISE W1 data (see the LS `DR9 bitmasks page`_) WISEMASK_W2 binary Bitwise mask for WISE W2 data (see the LS `DR9 bitmasks page`_) EBV float32 Galactic extinction E(B-V) reddening at pixel from `SFD98`_ PHOTSYS char[1] 'N' for an MzLS/BASS location, 'S' for a DECaLS location HPXPIXEL int64 HEALPixel containing this location at NSIDE=64 in the NESTED scheme ============= ======== ============== =================== Notes and Examples ================== See http://legacysurvey.org for more details about the corresponding columns for sources extracted by the Tractor in the Legacy Surveys, e.g. the units of the depth quantities. .. _`SFD98`: http://adsabs.harvard.edu/abs/1998ApJ...500..525S .. _`Legacy Surveys`: http://legacysurvey.org .. _`LS`: http://legacysurvey.org/dr9/catalogs/ .. _`DR9 bitmasks page`: https://www.legacysurvey.org/dr9/bitmasks/ .. _`desitarget data model`: https://desidatamodel.readthedocs.io/en/latest/DESI_TARGET/index.html .. _`DESI fiberassign code`: https://github.com/desihub/fiberassign