emline-SPECTROGRAPH-TILEID-GROUPID.fits¶

Summary:: This file records simple (Gaussian) emission line fits on the spectra for few major lines.
Naming Convention:: emline-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:: emline-[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, 188 KB

Contents¶

Number	EXTNAME	Type	Contents
HDU0		IMAGE	Empty
HDU1	EMLINEFIT	BINTABLE	Emission line fits table

FITS Header Units¶

HDU0¶

Empty HDU.

HDU1¶

EXTNAME = EMLINEFIT

Table with the emission line fit results for few major lines.

Required Header Keywords¶

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	345	int	width of table in bytes
NAXIS2	500	int	number of rows in table
RRFN	/global/cfs/cdirs/desi/spectro/redux/fuji/tiles/1x_depth/80608/5/redrock-1-80608-1xsubset5.fits	str	full path to the redrock file which contains the redshifts
COADDFN	/global/cfs/cdirs/desi/spectro/redux/fuji/tiles/1x_depth/80608/5/coadd-1-80608-1xsubset5.fits	str	full path to the coadd file which contains the spectra
RFHW	40	int	[Angstrom] rest-frame wavelength width used for fitting on each side of the line
MINRFHW	20	int	[Angstrom] minimum requested rest-frame width on each side of the line to consider the fitting
RFCONTW	200	int	[Angstrom] rest-frame wavelength extent to fit the continuum
RV	3.1	float	value of R_V to convert EBV to magnitudes
EMNAMES	OII,HDELTA,HGAMMA,HBETA,OIII,HALPHA	str	comma-separated list of emission lines to fit
RFWAVE00	3727.092,3729.874	str	[Angstrom] rest-frame, vacuum, wavelength for the first emission line to fit
RFWAVE01	4102.892	str	[Angstrom] rest-frame, vacuum, wavelength for the second emission line to fit
RFWAVE02	4341.684	str	[Angstrom] rest-frame, vacuum, wavelength for the third emission line to fit
RFWAVE03	4862.683	str	[Angstrom] rest-frame, vacuum, wavelength for the forth emission line to fit
RFWAVE04	4960.295,5008.239	str	[Angstrom] rest-frame, vacuum, wavelength for the fifth emission line to fit
RFWAVE05	6564.613	str	[Angstrom] rest-frame, vacuum, wavelength for the sixth emission line to fit

Required Data Table Columns¶

Name	Type	Units	Description
TARGETID	int64		Unique DESI target ID
Z	float64		Redshift measured by Redrock
ZWARN	int64		Redshift warning bitmask from Redrock
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
TARGET_RA	float64	deg	Target right ascension
TARGET_DEC	float64	deg	Target declination
OBJTYPE	char[3]		Object type: TGT, SKY, NON, BAD
OII_FLUX	float32	10**-17 erg/(s cm2)	Fitted flux for the [OII] doublet
OII_FLUX_IVAR	float32	10**+34 (s2 cm4) / erg2	Inverse variance of the fitted flux for the [OII] doublet
OII_SIGMA	float32	Angstrom	Fitted line width (in the observed frame) for the [OII] doublet
OII_SIGMA_IVAR	float32	Angstrom^-2	Inverse variance of the fitted line width (in the observed frame) for the [OII] doublet
OII_CONT	float32	10**-17 erg/(s cm2 Angstrom)	Continuum used for the fitting (fixed value) for the [OII] doublet
OII_CONT_IVAR	float32	10**+34 (s2 cm4 Angstrom2) / erg2	Inverse variance of the continuum for the [OII] doublet
OII_SHARE	float32		Fitted F1/(F0+F1) for the [OII] doublet, where F0 and F1 are the individual line fluxes
OII_SHARE_IVAR	float32		Inverse variance of the fitted F1/(F0+F1) for the [OII] doublet
OII_EW	float32	Angstrom	Fitted rest-frame equivalent width for the [OII] doublet
OII_EW_IVAR	float32	Angstrom^-2	Inverse variance of the fitted rest-frame equivalent width for the [OII] doublet
OII_CHI2	float32		Reduced chi2 of the fit for the [OII] doublet
OII_NDOF	int32		Number of degrees of freedom of the fit for the [OII] doublet
HDELTA_FLUX	float32	10**-17 erg/(s cm2)	Fitted flux for the HDELTA line
HDELTA_FLUX_IVAR	float32	10**+34 (s2 cm4) / erg2	Inverse variance of the fitted flux for the HDELTA line
HDELTA_SIGMA	float32	Angstrom	Fitted line width (in the observed frame) for the HDELTA line
HDELTA_SIGMA_IVAR	float32	Angstrom^-2	Inverse variance of the fitted line width (in the observed frame) for the HDELTA line
HDELTA_CONT	float32	10**-17 erg/(s cm2 Angstrom)	Continuum used for the fitting (fixed value) for the HDELTA line
HDELTA_CONT_IVAR	float32	10**+34 (s2 cm4 Angstrom2) / erg2	Inverse variance of the continuum for the HDELTA line
HDELTA_SHARE	float32		NaN (SHARE not relevant for HDELTA line)
HDELTA_SHARE_IVAR	float32		NaN (SHARE not relevant for HDELTA line)
HDELTA_EW	float32	Angstrom	Fitted rest-frame equivalent width for the HDELTA line
HDELTA_EW_IVAR	float32	Angstrom^-2	Inverse variance of the fitted rest-frame equivalent width for the HDELTA line
HDELTA_CHI2	float32		Reduced chi2 of the fit for the HDELTA line
HDELTA_NDOF	int32		Number of degrees of freedom of the fit for the HDELTA line
HGAMMA_FLUX	float32	10**-17 erg/(s cm2)	Fitted flux for the HGAMMA line
HGAMMA_FLUX_IVAR	float32	10**+34 (s2 cm4) / erg2	Inverse variance of the fitted flux for the HGAMMA line
HGAMMA_SIGMA	float32	Angstrom	Fitted line width (in the observed frame) for the HGAMMA line
HGAMMA_SIGMA_IVAR	float32	Angstrom^-2	Inverse variance of the fitted line width (in the observed frame) for the HGAMMA line
HGAMMA_CONT	float32	10**-17 erg/(s cm2 Angstrom)	Continuum used for the fitting (fixed value) for the HGAMMA line
HGAMMA_CONT_IVAR	float32	10**+34 (s2 cm4 Angstrom2) / erg2	Inverse variance of the continuum for the HGAMMA line
HGAMMA_SHARE	float32		NaN (SHARE not relevant for HGAMMA line)
HGAMMA_SHARE_IVAR	float32		NaN (SHARE not relevant for HGAMMA line)
HGAMMA_EW	float32	Angstrom	Fitted rest-frame equivalent width for the HGAMMA line
HGAMMA_EW_IVAR	float32	Angstrom^-2	Inverse variance of the fitted rest-frame equivalent width for the HGAMMA line
HGAMMA_CHI2	float32		Reduced chi2 of the fit for the HGAMMA line
HGAMMA_NDOF	int32		Number of degrees of freedom of the fit for the HGAMMA line
HBETA_FLUX	float32	10**-17 erg/(s cm2)	Fitted flux for the HBETA line
HBETA_FLUX_IVAR	float32	10**+34 (s2 cm4) / erg2	Inverse variance of the fitted flux for the HBETA line
HBETA_SIGMA	float32	Angstrom	Fitted line width (in the observed frame) for the HBETA line
HBETA_SIGMA_IVAR	float32	Angstrom^-2	Inverse variance of the fitted line width (in the observed frame) for the HBETA line
HBETA_CONT	float32	10**-17 erg/(s cm2 Angstrom)	Continuum used for the fitting (fixed value) for the HBETA line
HBETA_CONT_IVAR	float32	10**+34 (s2 cm4 Angstrom2) / erg2	Inverse variance of the continuum for the HBETA line
HBETA_SHARE	float32		NaN (SHARE not relevant for HBETA line)
HBETA_SHARE_IVAR	float32		NaN (SHARE not relevant for HBETA line)
HBETA_EW	float32	Angstrom	Fitted rest-frame equivalent width for the HBETA line
HBETA_EW_IVAR	float32	Angstrom^-2	Inverse variance of the fitted rest-frame equivalent width for the HBETA line
HBETA_CHI2	float32		Reduced chi2 of the fit for the HBETA line
HBETA_NDOF	int32		Number of degrees of freedom of the fit for the HBETA line
OIII_FLUX	float32	10**-17 erg/(s cm2)	Fitted flux for the [OIII] doublet
OIII_FLUX_IVAR	float32	10**+34 (s2 cm4) / erg2	Inverse variance of the fitted flux for the [OIII] doublet
OIII_SIGMA	float32	Angstrom	Fitted line width (in the observed frame) for the [OIII] doublet
OIII_SIGMA_IVAR	float32	Angstrom^-2	Inverse variance of the fitted line width (in the observed frame) for the [OIII] doublet
OIII_CONT	float32	10**-17 erg/(s cm2 Angstrom)	Continuum used for the fitting (fixed value) for the [OIII] doublet
OIII_CONT_IVAR	float32	10**+34 (s2 cm4 Angstrom2) / erg2	Inverse variance of the continuum for the [OIII] doublet
OIII_SHARE	float32		F1/(F0+F1) for the [OIII] doublet, where F0 and F1 are the individual line fluxes (SHARE value fixed during the fit)
OIII_SHARE_IVAR	float32		Infinite value, as SHARE is fixed during the fit
OIII_EW	float32	Angstrom	Fitted rest-frame equivalent width for the [OIII] doublet
OIII_EW_IVAR	float32	Angstrom^-2	Inverse variance of the fitted rest-frame equivalent width for the [OIII] doublet
OIII_CHI2	float32		Reduced chi2 of the fit for the [OIII] doublet
OIII_NDOF	int32		Number of degrees of freedom of the fit for the [OIII] doublet
HALPHA_FLUX	float32	10**-17 erg/(s cm2)	Fitted flux for the HALPHA line
HALPHA_FLUX_IVAR	float32	10**+34 (s2 cm4) / erg2	Inverse variance of the fitted flux for the HALPHA line
HALPHA_SIGMA	float32	Angstrom	Fitted line width (in the observed frame) for the HALPHA line
HALPHA_SIGMA_IVAR	float32	Angstrom^-2	Inverse variance of the fitted line width (in the observed frame) for the HALPHA line
HALPHA_CONT	float32	10**-17 erg/(s cm2 Angstrom)	Continuum used for the fitting (fixed value) for the HALPHA line
HALPHA_CONT_IVAR	float32	10**+34 (s2 cm4 Angstrom2) / erg2	Inverse variance of the continuum for the HALPHA line
HALPHA_SHARE	float32		NaN (SHARE not relevant for HALPHA line)
HALPHA_SHARE_IVAR	float32		NaN (SHARE not relevant for HALPHA line)
HALPHA_EW	float32	Angstrom	Fitted rest-frame equivalent width for the HALPHA line
HALPHA_EW_IVAR	float32	Angstrom^-2	Inverse variance of the fitted rest-frame equivalent width for the HALPHA line
HALPHA_CHI2	float32		Reduced chi2 of the fit for the HALPHA line
HALPHA_NDOF	int32		Number of degrees of freedom of the fit for the HALPHA line

Notes and Examples¶

The fit is done with the desispec.scripts.emline script.
[OII] is fit as a doublet (3927 and 3929), with the line ratio left free during the fit.
[OIII] is fit as a doublet (4960 and 5007), with the line ratio fixed during the fit.
The SHARE is fitted only for the [OII] doublet; for the [OIII] doublet, its value is fixed (hence the infinite OIII_SHARE_IVAR); for the other lines, the SHARE is not used, and NaN are reported.
If there are not enough pixels to fit or if the fit fails, NaN values are reported.
The default settings are designed for the ELGs (e.g. max_sigma); values to be interpreted with caution for the other targets.
The fitted flux is not forced to be positive, so negative values can happen.
The Z,ZWARN,SPECTYPE,DELTACHI2 (TARGET_RA,TARGET_DEC,OBJTYPE, respectively) columns come from the REDSHIFTS (FIBERMAP, respectively) extension of the input redrock file (see redrock-SPECTROGRAPH-TILEID-GROUPID).
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 the fuji (EDR) and guadalupe productions, the equivalent widths are wrong (overestimated) by a factor (1+Z) ** 2; the code bug has been corrected for subsequent productions (e.g. iron).