targets-dr7

Summary:

DESI target selection files contain a single binary table covering the entire footprint. They contain the variables used by target selection (e.g. fluxes), variables needed by fiber assignment (e.g. RA, DEC), and variables needed for traceability (e.g. TARGETFLAG, TARGETID).

Naming Convention:

DRX/VERSION/targets-DRX-VERSION.fits, where DRX is the imaging surveys data release name (e.g. dr7.1) and VERSION is the desitarget code version defining the cuts (e.g. 0.22.0).

Regex:

targets-dr[0.9]+\.[0-9]+-v?[0-9]+\.[0-9]+(\.[0-9]+|)\.fits

File Type:

FITS, 30 GB

Note: this documents the target catalog format starting with DR7 / desitarget 0.22.0 . The previous format is documented in targets-dr6.

Contents

Number	EXTNAME	Type	Contents
HDU0	PRIMARY	IMAGE	Empty
HDU1	TARGETS	BINTABLE	Target table

FITS Header Units

HDU0

EXTNAME = PRIMARY

This HDU has no non-standard required keywords.

Empty HDU.

HDU1

EXTNAME = TARGETS

Target selection table

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	374	int	width of table in bytes
NAXIS2	72660205	int	number of rows in table
OBSCON	DARK|GRAY	str
HPXNSIDE	64	int	HEALPix nside
HPXNEST	T	bool	HEALPix nested (not ring) ordering
SURVEY	main	str
RESOLVE	T	bool
MASKBITS	T	bool
FILENSID	64	int
FILENEST	T	bool
FILEHPX	5261	int

Required Data Table Columns

Name	Type	Units	Description
RELEASE	int16		Legacy Surveys (LS) Release
BRICKID	int32		Brick ID from tractor input
BRICKNAME	char[8]		Brick name from tractor input
BRICK_OBJID	int32		OBJID (unique to brick, but not to file)
MORPHTYPE	char[4]		Morphological Model type
RA	float64	deg	Right ascension [degrees]
DEC	float64	deg	Declination [degrees]
RA_IVAR	float32	deg**-2	Right ascension inverse variance [1/degrees**2]
DEC_IVAR	float32	deg**-2	Declination inverse variance [1/degrees**2]
DCHISQ	float32[5]		Difference in chi-squared between model fits
FLUX_G	float32		LS flux from tractor input (g)
FLUX_R	float32		LS flux from tractor input (r)
FLUX_Z	float32		LS flux from tractor input (z)
FLUX_W1	float32		WISE flux in W1
FLUX_W2	float32		WISE flux in W2
FLUX_W3	float32		WISE flux in W3
FLUX_W4	float32		WISE flux in W4
FLUX_IVAR_G	float32		Inverse Variance of FLUX_G
FLUX_IVAR_R	float32		Inverse Variance of FLUX_R
FLUX_IVAR_Z	float32		Inverse Variance of FLUX_Z
FLUX_IVAR_W1	float32		Inverse Variance of FLUX_W1
FLUX_IVAR_W2	float32		Inverse Variance of FLUX_W2
FLUX_IVAR_W3	float32		Inverse Variance of FLUX_W3
FLUX_IVAR_W4	float32		Inverse Variance of FLUX_W4
MW_TRANSMISSION_G	float32		Milky Way dust transmission in LS g
MW_TRANSMISSION_R	float32		Milky Way dust transmission in LS r
MW_TRANSMISSION_Z	float32		Milky Way dust transmission in LS z
MW_TRANSMISSION_W1	float32		Milky Way dust transmission in WISE W1
MW_TRANSMISSION_W2	float32		Milky Way dust transmission in WISE W2
MW_TRANSMISSION_W3	float32		Milky Way dust transmission in WISE W3
MW_TRANSMISSION_W4	float32		Milky Way dust transmission in WISE W4
NOBS_G	int16		Number of images for central pixel in LS g
NOBS_R	int16		Number of images for central pixel in LS r
NOBS_Z	int16		Number of images for central pixel in LS z
FRACFLUX_G	float32		Fraction of flux from other sources compared to this source in LS g
FRACFLUX_R	float32		Fraction of flux from other sources compared to this source in LS r
FRACFLUX_Z	float32		Fraction of flux from other sources compared to this source in LS z
FRACMASKED_G	float32		Fraction of pixels masked for this source in LS g
FRACMASKED_R	float32		Fraction of pixels masked for this source in LS r
FRACMASKED_Z	float32		Fraction of pixels masked for this source in LS z
FRACIN_G	float32		TODO: Description needed
FRACIN_R	float32		TODO: Description needed
FRACIN_Z	float32		TODO: Description needed
ALLMASK_G	int16		Bitwise mask for central pixel in LS g
ALLMASK_R	int16		Bitwise mask for central pixel in LS r
ALLMASK_Z	int16		Bitwise mask for central pixel in LS z
WISEMASK_W1	byte		Bitwise mask for WISE W1 data
WISEMASK_W2	byte		Bitwise mask for WISE W2 data
PSFDEPTH_G	float32		PSF-based depth in LS g
PSFDEPTH_R	float32		PSF-based depth in LS r
PSFDEPTH_Z	float32		PSF-based depth in LS z
GALDEPTH_G	float32		Galaxy model-based depth in LS g
GALDEPTH_R	float32		Galaxy model-based depth in LS r
GALDEPTH_Z	float32		Galaxy model-based depth in LS z
FRACDEV	float32		Fraction of model in deVaucouleurs profile
FRACDEV_IVAR	float32		Inverse variance of FRACDEV
SHAPEDEV_R	float32		Half-light radius of deVaucouleurs model
SHAPEDEV_R_IVAR	float32		Inverse variance of SHAPEDEV_R
SHAPEDEV_E1	float32		Ellipticity component 1 of deVaucouleurs model
SHAPEDEV_E1_IVAR	float32		Inverse variance of SHAPEDEV_E1
SHAPEDEV_E2	float32		Ellipticity component 2 of deVaucouleurs model
SHAPEDEV_E2_IVAR	float32		Inverse variance of SHAPEDEV_E2
SHAPEEXP_R	float32		Half-light radius of exponential model
SHAPEEXP_R_IVAR	float32		Inverse variance of SHAPEEXP_R
SHAPEEXP_E1	float32		Ellipticity component 1 of exponential model
SHAPEEXP_E1_IVAR	float32		Inverse variance of SHAPEEXP_E1
SHAPEEXP_E2	float32		Ellipticity component 2 of exponential model
SHAPEEXP_E2_IVAR	float32		Inverse variance of SHAPEEXP_E2
FIBERFLUX_G	float32		g-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber
FIBERFLUX_R	float32		r-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber
FIBERFLUX_Z	float32		z-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber
FIBERTOTFLUX_G	float32		like FIBERFLUX_G but including all objects overlapping this location
FIBERTOTFLUX_R	float32		like FIBERFLUX_R but including all objects overlapping this location
FIBERTOTFLUX_Z	float32		like FIBERFLUX_Z but including all objects overlapping this location
REF_CAT	char[2]		Reference catalog source for star: T2 for Tycho-2, G2 for Gaia DR2, L2 for the SGA, empty otherwise
REF_ID	int64		Tyc1*1,000,000+Tyc2*10+Tyc3 for Tycho-2; “sourceid” for Gaia DR2
GAIA_PHOT_G_MEAN_MAG	float32		Gaia G band magnitude
GAIA_PHOT_G_MEAN_FLUX_OVER_ERROR	float32		Gaia G band signal-to-noise
GAIA_PHOT_BP_MEAN_MAG	float32		Gaia BP band magnitude
GAIA_PHOT_BP_MEAN_FLUX_OVER_ERROR	float32		Gaia BP band signal-to-noise
GAIA_PHOT_RP_MEAN_MAG	float32		Gaia RP band magnitude
GAIA_PHOT_RP_MEAN_FLUX_OVER_ERROR	float32		Gaia RP band signal-to-noise
GAIA_PHOT_BP_RP_EXCESS_FACTOR	float32		Gaia BP/RP excess factor
GAIA_ASTROMETRIC_SIGMA5D_MAX	float32		Gaia longest semi-major axis of the 5-d error ellipsoid
GAIA_ASTROMETRIC_PARAMS_SOLVED	int64		Which astrometric parameters were estimated for a Gaia source
GAIA_ASTROMETRIC_EXCESS_NOISE	float32		Gaia astrometric excess noise
GAIA_DUPLICATED_SOURCE	bool		Gaia duplicated source flag
PARALLAX	float32		Reference catalog parallax
PARALLAX_IVAR	float32		Inverse variance of parallax
PMRA	float32		Reference catalog proper motion in the RA direction
PMRA_IVAR	float32		Inverse variance of PMRA
PMDEC	float32		Reference catalog proper motion in the Dec direction
PMDEC_IVAR	float32		Inverse variance of PMDEC
MASKBITS	int16		Bitwise mask from the imaging indicating potential issue or blending
EBV	float32		Median (average?) Milky Way dust E(B-V) extinction
PHOTSYS	char[1]		‘N’ for the MzLS/BASS photometric system, ‘S’ for DECaLS
TARGETID	int64		Unique targeting ID
DESI_TARGET	int64		DESI (dark time program) target selection bitmask
BGS_TARGET	int64		BGS (bright time program) target selection bitmask
MWS_TARGET	int64		MWS (bright time program) target selection bitmask
SUBPRIORITY	float64		Random subpriority [0-1] to break assignment ties
OBSCONDITIONS	int64		Flag the target to be observed in graytime.
PRIORITY_INIT	int64		Target initial priority from target selection bitmasks and OBSCONDITIONS
NUMOBS_INIT	int64		Initial number of observations for target calculated across target selection bitmasks and OBSCONDITIONS
HPXPIXEL	int64		HEALPixel containing target

Notes and Examples

In general, the above format contains:

• Columns that were used by target selection (e.g. FLUX_G/R/Z)

• Columns needed by fiber assignment (e.g. RA, DEC)

• Columns needed for traceability (e.g. BRICKNAME, TARGETID, DESI_TARGET, BGS_TARGET, MWS_TARGET)

FRACFLUX and FRACMASKED are profile-weighted quantities

SUBPRIORITY, PHOTSYS, TARGETID, DESI_TARGET, BGS_TARGET, MWS_TARGET and HPXPIXEL are created by target selection; the rest are passed through from the original input tractor or sweep files

See http://legacysurvey.org for more details about the columns from input tractor files