zmtl-SPECTROGRAPH-TILEID-thruGROUPID.fits

Summary:

The zmtl files contain information about redshifts used by the MTL (“Merged Target List”) process to update the observational state of targets in the MTL ledgers. In particular, the redshift information is crucial for deciding whether a target is a Lyman-alpha quasar that requires additional DESI observations.

Naming Convention:

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

Regex:

zmtl-[0-9]-[0-9]+-(thru|)[0-9]{8}\.fits

File Type:

FITS, 67 KB

Contents

Number	EXTNAME	Type	Contents
HDU0		IMAGE	Empty
HDU1	ZMTL	BINTABLE	Redshifts to inform MTL updates

FITS Header Units

HDU0

This HDU has no non-standard required keywords.

Empty HDU.

HDU1

EXTNAME = ZMTL

Redshifts to inform MTL updates

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	112	int	width of table in bytes
NAXIS2	500	int	number of rows in table
QN_ADDED	T	bool	True if QuasarNET information included
SQ_ADDED	F	bool	True if SQUEzE information included
AB_ADDED	F	bool	True if absorption line information included
ZC_ADDED	F	bool	True if combined redshift information included
QNMODFIL	/global/cfs/cdirs/desi/target/catalogs/lya/qn_models/qn_train_coadd_indtrain_0_0_boss10.h5	str	Filename of QuasarNET model
BADPTLQA	F	bool	True if all fibers on a petal were masked

Required Data Table Columns

Name	Type	Units	Description
RA	float64	deg	Target Right Ascension
DEC	float64	deg	Target declination
TARGETID	int64		Unique DESI target ID
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
SV3_DESI_TARGET [1]	int64		DESI (dark time program) target selection bitmask for SV3
SV3_BGS_TARGET [1]	int64		BGS (bright time program) target selection bitmask for SV3
SV3_MWS_TARGET [1]	int64		MWS (bright time program) target selection bitmask for SV3
SV3_SCND_TARGET [1]	int64		Secondary target selection bitmask for SV3
DESI_TARGET [1]	int64		DESI (dark time program) target selection bitmask
BGS_TARGET [1]	int64		BGS (Bright Galaxy Survey) target selection bitmask
MWS_TARGET [1]	int64		Milky Way Survey targeting bits
SCND_TARGET [1]	int64		Target selection bitmask for secondary programs
Z	float64		Redshift measured by Redrock
ZWARN	int64		Redshift warning bitmask from Redrock, plus DESI-specific bits set
SPECTYPE	char[6]		Spectral type of Redrock best fit template (e.g. GALAXY, QSO, STAR)
DELTACHI2	float64		chi2 difference between first- and second-best redrock template fits
NUMOBS	int32		Number of spectroscopic observations (on this specific, single tile)
ZTILEID	int32		ID of tile that most recently updated target’s state
Z_QN	float64		Redshift measured by QuasarNET
Z_QN_CONF	float64		Redshift confidence from QuasarNET
IS_QSO_QN	int16		Spectroscopic classification from QuasarNET (1 for a quasar)

[1] (1,2,3,4,5,6,7,8,9,10,11,12)

Only either the four SV1, SV3 or Main Survey columns will be present. TARGET bitmask columns are preceded by the survey PHASE except in the case of Main Survey files (i.e. DESI_TARGET is called SV1_DESI_TARGET when the survey PHASE is sv1).

Notes and Examples

See the DESI Survey Operations paper (Schlafly et al., in preparation) for details of how the quantities in the zmtl files are used to update the observational state of a target in the MTL ledgers.

For more information, see QuasarNET for QuasarNET and SQUEzE for SQUEzE.