redrock-SPECTROGRAPH-TILEID-GROUPID.fits

Summary:

Redshifts and spectral classifications from Redrock.

Naming Convention:

redrock-SPECTROGRAPH-TILEID-GROUPID.fits, where SPECTROGRAPH is the spectrograph ID, TILEID is the tile number and GROUPID depends on the GROUPTYPE of the tile coadd.

Regex:

redrock-[0-9]-[0-9]+-([14]xsubset[1-6]|lowspeedsubset[1-6]|exp[0-9]{8}|thru[0-9]{8}|[0-9]{8})\.fits

File Type:

FITS, 450 KB

This file contains spectral classifications and redshifts for spectra coadded across exposures of an individual tile. For a similar file that also combined data across multiple tiles, see healpix-based Redrock files.

Contents

Number

EXTNAME

Type

Contents

HDU0

IMAGE

Keywords only

HDU1

REDSHIFTS

BINTABLE

Table with redshifts and spectral classifications

HDU2

FIBERMAP

BINTABLE

Target photometry, metadata, and what fibers they are assigned to

HDU3

EXP_FIBERMAP

BINTABLE

Per-exposure entries from input fibermaps

HDU4

TSNR2

BINTABLE

Template signal-to-noise values from input coadd SCORES table

FITS Header Units

HDU0

Required Header Keywords

Required Header Keywords Table

KEY

Example Value

Type

Comment

LONGSTRN

OGIP 1.0

str

RRVER

0.15.0

str

Redrock version

TEMNAM00

GALAXY

str

Redrock template 00 name

TEMVER00

2.6

str

Redrock template 00 version

TEMNAM01

QSO

str

TEMVER01

0.1

str

TEMNAM02

STAR:::A

str

TEMVER02

0.1

str

TEMNAM03

STAR:::B

str

TEMVER03

0.1

str

TEMNAM04

STAR:::CV

str

TEMVER04

0.1

str

TEMNAM05

STAR:::F

str

TEMVER05

0.1

str

TEMNAM06

STAR:::G

str

TEMVER06

0.1

str

TEMNAM07

STAR:::K

str

TEMVER07

0.1

str

TEMNAM08

STAR:::M

str

TEMVER08

0.1

str

TEMNAM09

STAR:::WD

str

TEMVER09

0.1

str

SPGRP

cumulative

str

Exposure grouping (pernight, cumulative, …)

SPGRPVAL

20210205

int

Value of grouping (night, expid, …)

TILEID

80605

int

DESI Tile ID

SPECTRO

6

int

Spectrograph number

PETAL

6

int

Focal plane petal number (same as SPECTRO)

NIGHT [1]

20210205

int

(Last) night of data included, if applicable to grouping

Empty HDU.

HDU1

EXTNAME = REDSHIFTS

Spectral classifications and redshifts from Redrock.

Required Header Keywords

Required Header Keywords Table

KEY

Example Value

Type

Comment

NAXIS1

170

int

Width of table in bytes

NAXIS2

500

int

Number of targets in table

Required Data Table Columns

Name

Type

Units

Description

TARGETID

int64

Unique DESI target ID

CHI2

float64

Best fit chi squared

COEFF

float64[10]

Redrock template coefficients

Z

float64

Redshift measured by Redrock

ZERR

float64

Redshift error from redrock

ZWARN

int64

Redshift warning bitmask from Redrock

NPIXELS

int64

Number of unmasked pixels contributing to the Redrock fit

SPECTYPE

char[6]

Spectral type of Redrock best fit template (e.g. GALAXY, QSO, STAR)

SUBTYPE

char[20]

Spectral subtype

NCOEFF

int64

Number of Redrock template coefficients

DELTACHI2

float64

chi2 difference between first- and second-best redrock template fits

HDU2

EXTNAME = FIBERMAP

Fibermap with target metadata such as photometry, target selection bits, and what fibers each target was assigned to. This table is row-matched to the REDSHIFTS table.

Required Header Keywords

Required Header Keywords Table

KEY

Example Value

Type

Comment

NAXIS1

371

int

Width of table in bytes

NAXIS2

500

int

Number of targets in table.

Required Data Table Columns

Name

Type

Units

Description

TARGETID

int64

Unique DESI target ID

PETAL_LOC

int16

Petal location [0-9]

DEVICE_LOC

int32

Device location on focal plane [0-523]

LOCATION

int64

Location on the focal plane PETAL_LOC*1000 + DEVICE_LOC

FIBER

int32

Fiber ID on the CCDs [0-4999]

COADD_FIBERSTATUS

int32

bitwise-AND of input FIBERSTATUS

TARGET_RA

float64

deg

Barycentric right ascension in ICRS

TARGET_DEC

float64

deg

Barycentric declination in ICRS

PMRA

float32

mas yr^-1

proper motion in the +RA direction (already including cos(dec))

PMDEC

float32

mas yr^-1

Proper motion in the +Dec direction

REF_EPOCH

float32

yr

Reference epoch for Gaia/Tycho astrometry. Typically 2015.5 for Gaia

LAMBDA_REF

float32

Angstrom

Requested wavelength at which targets should be centered on fibers

FA_TARGET

int64

Targeting bit internally used by fiberassign (linked with FA_TYPE)

FA_TYPE

binary

Fiberassign internal target type (science, standard, sky, safe, suppsky)

OBJTYPE

char[3]

Object type: TGT, SKY, NON, BAD

FIBERASSIGN_X

float32

mm

Fiberassign expected CS5 X location on focal plane

FIBERASSIGN_Y

float32

mm

Fiberassign expected CS5 Y location on focal plane

PRIORITY

int32

Target current priority

SUBPRIORITY

float64

Random subpriority [0-1) to break assignment ties

OBSCONDITIONS

int32

Bitmask of allowed observing conditions

RELEASE

int16

Imaging surveys release ID

BRICKNAME

char[8]

Brick name from tractor input

BRICKID

int32

Brick ID from tractor input

BRICK_OBJID

int32

Imaging Surveys OBJID on that brick

MORPHTYPE

char[4]

Imaging Surveys morphological type from Tractor

EBV

float32

mag

Galactic extinction E(B-V) reddening from SFD98

FLUX_G

float32

nanomaggy

Flux in the Legacy Survey g-band (AB)

FLUX_R

float32

nanomaggy

Flux in the Legacy Survey r-band (AB)

FLUX_Z

float32

nanomaggy

Flux in the Legacy Survey z-band (AB)

FLUX_W1

float32

nanomaggy

WISE flux in W1 (AB)

FLUX_W2

float32

nanomaggy

WISE flux in W2 (AB)

FLUX_IVAR_G

float32

nanomaggy^-2

Inverse variance of FLUX_G (AB)

FLUX_IVAR_R

float32

nanomaggy^-2

Inverse variance of FLUX_R (AB)

FLUX_IVAR_Z

float32

nanomaggy^-2

Inverse variance of FLUX_Z (AB)

FLUX_IVAR_W1

float32

nanomaggy^-2

Inverse variance of FLUX_W1 (AB)

FLUX_IVAR_W2

float32

nanomaggy^-2

Inverse variance of FLUX_W2 (AB)

FIBERFLUX_G

float32

nanomaggy

Predicted g-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing

FIBERFLUX_R

float32

nanomaggy

Predicted r-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing

FIBERFLUX_Z

float32

nanomaggy

Predicted z-band flux within a fiber of diameter 1.5 arcsec from this object in 1 arcsec Gaussian seeing

FIBERTOTFLUX_G

float32

nanomaggy

Predicted g-band flux within a fiber of diameter 1.5 arcsec from all sources at this location in 1 arcsec Gaussian seeing

FIBERTOTFLUX_R

float32

nanomaggy

Predicted r-band flux within a fiber of diameter 1.5 arcsec from all sources at this location in 1 arcsec Gaussian seeing

FIBERTOTFLUX_Z

float32

nanomaggy

Predicted z-band flux within a fiber of diameter 1.5 arcsec from all sources at this location in 1 arcsec Gaussian seeing

MASKBITS

int16

Bitwise mask from the imaging indicating potential issue or blending

SERSIC

float32

Power-law index for the Sersic profile model (MORPHTYPE=”SER”)

SHAPE_R

float32

arcsec

Half-light radius of galaxy model (>0)

SHAPE_E1

float32

Ellipticity component 1 of galaxy model for galaxy type MORPHTYPE

SHAPE_E2

float32

Ellipticity component 2 of galaxy model for galaxy type MORPHTYPE

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_BP_MEAN_MAG

float32

mag

Gaia BP band magnitude

GAIA_PHOT_RP_MEAN_MAG

float32

mag

Gaia RP band magnitude

PARALLAX

float32

mas

Reference catalog parallax

PHOTSYS

char[1]

‘N’ for the MzLS/BASS photometric system, ‘S’ for DECaLS

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

SV1_DESI_TARGET [1]

int64

DESI (dark time program) target selection bitmask for SV1

SV1_BGS_TARGET [1]

int64

BGS (bright time program) target selection bitmask for SV1

SV1_MWS_TARGET [1]

int64

MWS (bright time program) target selection bitmask for SV1

SV1_SCND_TARGET [1]

int64

Secondary target selection bitmask for SV1

DESI_TARGET

int64

DESI (dark time program) target selection bitmask

BGS_TARGET

int64

BGS (Bright Galaxy Survey) target selection bitmask

MWS_TARGET

int64

Milky Way Survey targeting bits

SCND_TARGET [1]

int64

Target selection bitmask for secondary programs

PLATE_RA

float64

deg

Barycentric Right Ascension in ICRS to be used by PlateMaker

PLATE_DEC

float64

deg

Barycentric Declination in ICRS to be used by PlateMaker

TILEID

int32

Unique DESI tile ID

COADD_NUMEXP

int16

Number of exposures in coadd

COADD_EXPTIME

float32

s

Summed exposure time for coadd

COADD_NUMNIGHT

int16

Number of nights in coadd

COADD_NUMTILE

int16

Number of tiles in coadd

MEAN_DELTA_X

float32

mm

Mean (over exposures) fiber difference requested - actual CS5 X location on focal plane

RMS_DELTA_X

float32

mm

RMS (over exposures) of the fiber difference between measured and requested CS5 X location on focal plane

MEAN_DELTA_Y

float32

mm

Mean (over exposures) fiber difference requested - actual CS5 Y location on focal plane

RMS_DELTA_Y

float32

mm

RMS (over exposures) of the fiber difference between measured and requested CS5 Y location on focal plane

MEAN_FIBER_RA

float64

deg

Mean (over exposures) RA of actual fiber position

STD_FIBER_RA

float32

arcsec

Standard deviation (over exposures) of RA of actual fiber position

MEAN_FIBER_DEC

float64

deg

Mean (over exposures) DEC of actual fiber position

STD_FIBER_DEC

float32

arcsec

Standard deviation (over exposures) of DEC of actual fiber position

MEAN_PSF_TO_FIBER_SPECFLUX

float32

Mean of input exposures fraction of light from point-like source captured by 1.5 arcsec diameter fiber given atmospheric seeing

MEAN_FIBER_X

float32

mm

Mean (over exposures) fiber CS5 X location on focal plane

MEAN_FIBER_Y

float32

mm

Mean (over exposures) fiber CS5 Y location on focal plane

HDU3

EXTNAME = EXP_FIBERMAP

Fibermap entries that vary from exposure to exposure, e.g. what exposures were include in the coadd and what focalplane (x,y) each target was located at for each exposure.

Required Header Keywords

Required Header Keywords Table

KEY

Example Value

Type

Comment

NAXIS1

162

int

Width of table in bytes

NAXIS2

500

int

Number of input target-exposures = rows in table

Required Data Table Columns

Name

Type

Units

Description

TARGETID

int64

Unique DESI target ID

PRIORITY

int32

Target current priority

SUBPRIORITY

float64

Random subpriority [0-1) to break assignment ties

NIGHT

int32

EXPID

int32

DESI Exposure ID number

MJD

float64

Modified Julian Date when shutter was opened for this exposure

TILEID

int32

Unique DESI tile ID

EXPTIME

float64

s

Length of time shutter was open

PETAL_LOC

int16

Petal location [0-9]

DEVICE_LOC

int32

Device location on focal plane [0-523]

LOCATION

int64

Location on the focal plane PETAL_LOC*1000 + DEVICE_LOC

FIBER

int32

Fiber ID on the CCDs [0-4999]

FIBERSTATUS

int32

Fiber status mask. 0=good

FIBERASSIGN_X

float32

mm

Fiberassign expected CS5 X location on focal plane

FIBERASSIGN_Y

float32

mm

Fiberassign expected CS5 Y location on focal plane

LAMBDA_REF

float32

Angstrom

Requested wavelength at which targets should be centered on fibers

PLATE_RA

float64

deg

Barycentric Right Ascension in ICRS to be used by PlateMaker

PLATE_DEC

float64

deg

Barycentric Declination in ICRS to be used by PlateMaker

NUM_ITER

int64

Number of positioner iterations

FIBER_X

float64

mm

CS5 X location requested by PlateMaker

FIBER_Y

float64

mm

CS5 Y location requested by PlateMaker

DELTA_X

float64

mm

CS5 X requested minus actual position

DELTA_Y

float64

mm

CS5 Y requested minus actual position

FIBER_RA

float64

deg

RA of actual fiber position

FIBER_DEC

float64

deg

DEC of actual fiber position

PSF_TO_FIBER_SPECFLUX

float64

fraction of light from point-like source captured by 1.5 arcsec diameter fiber given atmospheric seeing

HDU4

EXTNAME = TSNR2

Template signal-to-noise squared. These quantities weight the observed (S/N)^2 by which wavelengths matter most for different target types, e.g. QSOs weight blue wavelengths more while ELGs weight redder wavelengths more due to the wavelengths of the observed emission lines. For more details, see section 4.14 of Guy et al 2023.

This table is row-matched to the REDSHIFTS table.

Required Header Keywords

Required Header Keywords Table

KEY

Example Value

Type

Comment

NAXIS1

136

int

Width of table in bytes.

NAXIS2

500

int

Number of targets = number of table rows.

Required Data Table Columns

Name

Type

Units

Description

TARGETID

int64

Unique DESI target ID

TSNR2_GPBDARK_B

float32

TSNR2_ELG_B

float32

ELG B template (S/N)^2

TSNR2_GPBBRIGHT_B

float32

TSNR2_LYA_B

float32

LYA B template (S/N)^2

TSNR2_BGS_B

float32

BGS B template (S/N)^2

TSNR2_GPBBACKUP_B

float32

TSNR2_QSO_B

float32

QSO B template (S/N)^2

TSNR2_LRG_B

float32

LRG B template (S/N)^2

TSNR2_GPBDARK_R

float32

TSNR2_ELG_R

float32

ELG R template (S/N)^2

TSNR2_GPBBRIGHT_R

float32

TSNR2_LYA_R

float32

LYA R template (S/N)^2

TSNR2_BGS_R

float32

BGS R template (S/N)^2

TSNR2_GPBBACKUP_R

float32

TSNR2_QSO_R

float32

QSO R template (S/N)^2

TSNR2_LRG_R

float32

LRG R template (S/N)^2

TSNR2_GPBDARK_Z

float32

TSNR2_ELG_Z

float32

ELG Z template (S/N)^2

TSNR2_GPBBRIGHT_Z

float32

TSNR2_LYA_Z

float32

LYA Z template (S/N)^2

TSNR2_BGS_Z

float32

BGS Z template (S/N)^2

TSNR2_GPBBACKUP_Z

float32

TSNR2_QSO_Z

float32

QSO Z template (S/N)^2

TSNR2_LRG_Z

float32

LRG Z template (S/N)^2

TSNR2_GPBDARK

float32

TSNR2_ELG

float32

ELG template (S/N)^2 summed over B,R,Z

TSNR2_GPBBRIGHT

float32

TSNR2_LYA

float32

LYA template (S/N)^2 summed over B,R,Z

TSNR2_BGS

float32

BGS template (S/N)^2 summed over B,R,Z

TSNR2_GPBBACKUP

float32

TSNR2_QSO

float32

QSO template (S/N)^2 summed over B,R,Z

TSNR2_LRG

float32

LRG template (S/N)^2 summed over B,R,Z

Notes and Examples

The REDSHIFTS, FIBERMAP, and TSNR2 tables are row-matched with one row per target. They also include a TARGETID column for confirmation and database-like joins with other tables. The EXP_FIBERMAP HDU has one row per target-exposure, and thus will have multiple entries per target when a target was observed on multiple input exposures.

This file is for redshifts from an individual spectrograph/petal of an individual tile. For a contatenation of all such files within a given survey and program, see the ztile file.

For the SURVEY=cmx m33 tile (TILEID=80615) tile and all the SURVEY=sv1 tiles (except TILEID=80971-80976, the dc3r2 ones), proper-motion correction was applied at the fiberassign design step; thus the following columns can have different values than in the desitarget products: TARGET_RA, TARGET_DEC, REF_EPOCH, PLATE_RA, PLATE_DEC, and PLATE_REF_EPOCH.

For targets with a non-zero proper motion, FIBER_RA and FIBER_DEC refer to the position at the reference epoch (but note that the proper-motion correction has been applied at the time of the observation, it is just not recorded in FIBER_RA and FIBER_DEC).