qso_qn-SPECTROGRAPH-TILEID-GROUPID.fits

Summary:

This file contains the output of QuasarNet (QSO classification algorithm and redshift fitter). When there is a disagreement between the redshift from QN and Redrock, a new redshift is fitted using only QSO templates and redshift from QN as prior.

Naming Convention:

qso_qn-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:

qso_qn-[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, 33 KB

Contents

Number	EXTNAME	Type	Contents
HDU0		IMAGE	Empty.
HDU1	QN_RR	BINTABLE	Output of QuasarNet afterburner.

FITS Header Units

HDU0

This HDU has no non-standard required keywords.

Empty HDU.

HDU1

EXTNAME = QN_RR

Contains the result of QuasarNet afterburner and the new redshift fit from run of Redrock with QSO templates and redshift prior from QuasarNet.

Required Header Keywords

Required Header Keywords Table

KEY	Example Value	Type	Comment
NAXIS1	151	int	width of table in bytes
NAXIS2	155	int	number of rows in table

Required Data Table Columns

Name	Type	Units	Description
TARGETID	int64		Unique DESI target ID
RA	float64	deg	Target Right Ascension
DEC	float64	deg	Target declination
Z_NEW	float64		New redshift computed with redrock with QN prior and only qso templates
ZERR_NEW	float32		Redshift error from the new run of redrock
SV1_DESI_TARGET [1]	int64		DESI (dark time program) target selection bitmask for SV1
DESI_TARGET [1]	int64		DESI (dark time program) target selection bitmask
COEFFS	float32[10]		Coefficient of the fit for the new run of redrock
SPECTYPE	char[10]		Spectral type of Redrock best fit template (e.g. GALAXY, QSO, STAR)
Z_RR	float32		Redshift collected from redrock file
Z_QN	float32		Redshift measured by QuasarNET using line with highest confidence
IS_QSO_QN_NEW_RR	logical		QN identified as QSO at different redshift or classification than Redrock
C_LYA	float32		Confidence for LyA line, i.e. ~probability to be a QSO
C_CIV	float32		Confidence for CIV line
C_CIII	float32		Confidence for CIII line
C_MgII	float32		Confidence for MgII line
C_Hbeta	float32		Confidence for Hbeta line
C_Halpha	float32		Confidence for Halpha line
Z_LYA	float32		Redshift estimated by QuasarNET with LyA line
Z_CIV	float32		Redshift estimated by QuasarNET with CIV line
Z_CIII	float32		Redshift estimated by QuasarNET with CIII line
Z_MgII	float32		Redshift estimated by QuasarNET with MgII line
Z_Hbeta	float32		Redshift estimated by QuasarNET with Hbeta line
Z_Halpha	float32		Redshift estimated by QuasarNET with Halpha line

[1] (1,2)

Optional

Notes:

IS_QSO_QN_NEW_RR is set if QuasarNET selects this as a QSO and the answer is different from Redrock, either because Redrock didn’t identify it as a QSO or because the Redrock redshift differed by more than 0.05. If both QuasarNET and Redrock agree that it is a QSO and agree on the redshift, then IS_QSO_QN_NEW_RR=False.

The QuasarNET QSO selection is performed with the C_XXX confidence parameters. IS_QSO_QN_NEW_RR uses a relatively loose cut of max(C_XXX) >= 0.5; downstream code may choose to use a tighter cut.

Notes and Examples

These files are generated with https://github.com/desihub/desispec/blob/main/bin/desi_qso_qn_afterburner