targets-dr8¶
- Summary:
DESI target selection files include a single binary table containing the targets in a (nested) HEALPixel. 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. DESITARGET, TARGETID).
- Naming Convention:
PHASEtargets-OBSCON-RESOLVE-hp-HP.fits
, wherePHASE
is a specific DESI observational phase (e.g. svX with X=1,2 for iterations of Survey Validation),OBSCON
is the observing condition (or “layer”) for the targets (e.g. dark),RESOLVE
is “noresolve” for targets that are not resolved, andHP
is the HEALPixel covered by the file at the (nested) HEALPixel nside included in the file header asFILENSID
(e.g. 11). For targets that are not resolvedRESOLVE
is omitted from the filename. For targets that are part of the DESI Main Science SurveyPHASE
is omitted from the filename.- Regex:
.*?target-.*?-hp-?[0-9]+\.fits
- File Type:
FITS, 2 GB
Note: this documents the target catalog format starting with DR8 / desitarget 0.31.0 . The previous format is documented in targets-dr7.
Examples¶
For research notes detailing early target selections for DESI, target files are available at:
Contents¶
Number |
EXTNAME |
Type |
Contents |
---|---|---|---|
PRIMARY |
IMAGE |
Empty |
|
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 |
observing layer for file |
HPXNSIDE |
64 |
int |
HEALPix nside for column HPXPIXEL |
HPXNEST |
T |
bool |
HEALPix nested (not ring) ordering |
SURVEY |
main |
str |
sv1 for SV, main for Main Survey |
RESOLVE |
T |
bool |
|
MASKBITS |
T |
bool |
|
SUPP |
F |
bool |
|
TCNAMES |
“QSO,LRG” |
str |
run for this target-class subset |
FILENSID |
2 |
int |
HEALPix nside covered by file |
FILENEST |
T |
bool |
HEALPix nested (not ring) ordering |
FILEHPX |
11 |
int |
HEALPix pixel(s) covered by file |
Required Data Table Columns¶
Name |
Type |
Units |
Description |
---|---|---|---|
RELEASE |
int16 |
||
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] |
RA_IVAR |
float32 |
deg**-2 |
Right ascension inverse variance [1/degrees**2] |
DEC |
float64 |
deg |
Declination [degrees] |
DEC_IVAR |
float32 |
deg**-2 |
Declination inverse variance [1/degrees**2] |
DCHISQ |
float32[5] |
Difference in chi-squared between model fits |
|
EBV |
float32 |
mag |
Galactic extinction E(B-V) reddening from SFD98 |
FLUX_G |
float32 |
nanomaggy |
LS flux from tractor input (g) |
FLUX_R |
float32 |
nanomaggy |
LS flux from tractor input (r) |
FLUX_Z |
float32 |
nanomaggy |
LS flux from tractor input (z) |
FLUX_IVAR_G |
float32 |
nanomaggy**-2 |
Inverse Variance of FLUX_G |
FLUX_IVAR_R |
float32 |
nanomaggy**-2 |
Inverse Variance of FLUX_R |
FLUX_IVAR_Z |
float32 |
nanomaggy**-2 |
Inverse Variance of FLUX_Z |
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 |
|
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 |
Fraction of a source’s flux within a LS blob in g |
|
FRACIN_R |
float32 |
Fraction of a source’s flux within a LS blob in r |
|
FRACIN_Z |
float32 |
Fraction of a source’s flux within a LS blob in z |
|
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 |
|
PSFDEPTH_G |
float32 |
nanomaggy**-2 |
PSF-based depth in LS g |
PSFDEPTH_R |
float32 |
nanomaggy**-2 |
PSF-based depth in LS r |
PSFDEPTH_Z |
float32 |
nanomaggy**-2 |
PSF-based depth in LS z |
GALDEPTH_G |
float32 |
nanomaggy**-2 |
Galaxy model-based depth in LS g |
GALDEPTH_R |
float32 |
nanomaggy**-2 |
Galaxy model-based depth in LS r |
GALDEPTH_Z |
float32 |
nanomaggy**-2 |
Galaxy model-based depth in LS z |
FLUX_W1 |
float32 |
nanomaggy |
WISE flux in W1 (AB system) |
FLUX_W2 |
float32 |
nanomaggy |
WISE flux in W2 (AB) |
FLUX_W3 |
float32 |
nanomaggy |
WISE flux in W3 (AB) |
FLUX_W4 |
float32 |
nanomaggy |
WISE flux in W4 (AB) |
FLUX_IVAR_W1 |
float32 |
nanomaggy**-2 |
Inverse Variance of FLUX_W1 (AB system) |
FLUX_IVAR_W2 |
float32 |
nanomaggy**-2 |
Inverse Variance of FLUX_W2 (AB) |
FLUX_IVAR_W3 |
float32 |
nanomaggy**-2 |
Inverse Variance of FLUX_W3 (AB) |
FLUX_IVAR_W4 |
float32 |
nanomaggy**-2 |
Inverse Variance of FLUX_W4 (AB) |
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 |
|
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 |
|
FIBERFLUX_G |
float32 |
nanomaggy |
g-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber |
FIBERFLUX_R |
float32 |
nanomaggy |
r-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber |
FIBERFLUX_Z |
float32 |
nanomaggy |
z-band object model flux for 1 arcsec seeing and 1.5 arcsec diameter fiber |
FIBERTOTFLUX_G |
float32 |
nanomaggy |
like FIBERFLUX_G but including all objects overlapping this location |
FIBERTOTFLUX_R |
float32 |
nanomaggy |
like FIBERFLUX_R but including all objects overlapping this location |
FIBERTOTFLUX_Z |
float32 |
nanomaggy |
like FIBERFLUX_Z but including all objects overlapping this location |
REF_EPOCH |
float32 |
yr |
reference epoch for Gaia/Tycho astrometry. Typically 2015.5 for Gaia. |
WISEMASK_W1 |
byte |
W1 bitmask as cataloged on the LS DR8 bitmasks page |
|
WISEMASK_W2 |
byte |
W2 bitmask as cataloged on the LS DR8 bitmasks page |
|
MASKBITS |
int16 |
bitmask for |
|
FRACDEV |
float32 |
Fraction of model in deVaucouleurs profile |
|
FRACDEV_IVAR |
float32 |
Inverse variance of FRACDEV |
|
SHAPEDEV_R |
float32 |
arcsec |
Half-light radius of deVaucouleurs model |
SHAPEDEV_E1 |
float32 |
Ellipticity component 1 of deVaucouleurs model |
|
SHAPEDEV_E2 |
float32 |
Ellipticity component 2 of deVaucouleurs model |
|
SHAPEDEV_R_IVAR |
float32 |
arcsec**-2 |
Inverse variance of SHAPEDEV_R |
SHAPEDEV_E1_IVAR |
float32 |
Inverse variance of SHAPEDEV_E1 |
|
SHAPEDEV_E2_IVAR |
float32 |
Inverse variance of SHAPEDEV_E2 |
|
SHAPEEXP_R |
float32 |
arcsec |
Half-light radius of exponential model |
SHAPEEXP_E1 |
float32 |
Ellipticity component 1 of exponential model |
|
SHAPEEXP_E2 |
float32 |
Ellipticity component 2 of exponential model |
|
SHAPEEXP_R_IVAR |
float32 |
arcsec**-2 |
Inverse variance of SHAPEEXP_R |
SHAPEEXP_E1_IVAR |
float32 |
Inverse variance of SHAPEEXP_E1 |
|
SHAPEEXP_E2_IVAR |
float32 |
Inverse variance of SHAPEEXP_E2 |
|
REF_ID |
int64 |
Tyc1*1,000,000+Tyc2*10+Tyc3 for Tycho-2; “sourceid” for Gaia DR2 |
|
REF_CAT |
char[2] |
Reference catalog source for star: “T2” for Tycho-2, “G2” for Gaia DR2, “L2” for the SGA, empty otherwise |
|
GAIA_PHOT_G_MEAN_MAG |
float32 |
mag |
Gaia G band magnitude |
GAIA_PHOT_G_MEAN_FLUX_OVER_ERROR |
float32 |
Gaia G band signal-to-noise |
|
GAIA_PHOT_BP_MEAN_MAG |
float32 |
mag |
Gaia BP band magnitude |
GAIA_PHOT_BP_MEAN_FLUX_OVER_ERROR |
float32 |
Gaia BP band signal-to-noise |
|
GAIA_PHOT_RP_MEAN_MAG |
float32 |
mag |
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_EXCESS_NOISE |
float32 |
Gaia astrometric excess noise |
|
GAIA_DUPLICATED_SOURCE |
bool |
Gaia duplicated source flag |
|
GAIA_ASTROMETRIC_SIGMA5D_MAX |
float32 |
mas |
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 |
|
PARALLAX |
float32 |
mas |
Reference catalog parallax |
PARALLAX_IVAR |
float32 |
mas**-2 |
Inverse variance of parallax |
PMRA |
float32 |
mas/yr |
Reference catalog proper motion in the RA direction |
PMRA_IVAR |
float32 |
mas/yr**-2 |
Inverse variance of PMRA |
PMDEC |
float32 |
mas/yr |
Reference catalog proper motion in the Dec direction |
PMDEC_IVAR |
float32 |
mas/yr**-2 |
Inverse variance of PMDEC |
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 target to be observed in combinations of dark/gray/bright observing layer |
|
PRIORITY_INIT |
int64 |
Initial priority for target calculated across 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 at HPXNSIDE |
Notes¶
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, OBSCONDITIONS, PRIORITY_INIT, NUMOBS_INIT, PHOTSYS, TARGETID, DESI_TARGET, BGS_TARGET, MWS_TARGET and HPXPIXEL are created by target selection; the rest are passed through from the original LS tractor or sweep files.
See https://www.legacysurvey.org for more details about columns in the data model.