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Glossary of WSA attributes
This Glossary alphabetically lists all attributes used in the UKIDSSDR3 database(s) held in the WSA. If you would like to have more information about the schema tables please use the UKIDSSDR3 Schema Browser (other Browser versions).

A

B

C

D

E

F

G

H

I

J

K

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M

N

O

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Q

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J
Name	Schema Table	Database	Description	Type	Length	Unit	Default Value	Unified Content Descriptor
j_1AperMag3	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Default point/extended source 1st epoch J aperture corrected mag (2.0 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
j_1AperMag3	lasSource	WSA	Default point/extended source 1st epoch J aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator	real	4	mag	-0.9999995e9	PHOT_MAG
j_1AperMag3Err	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in default point/extended source 1st epoch J mag (2.0 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
j_1AperMag4	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source 1st epoch J aperture corrected mag (2.8 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
j_1AperMag4Err	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in extended source 1st epoch J mag (2.8 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
j_1AperMag6	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source 1st epoch J aperture corrected mag (5.7 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
j_1AperMag6Err	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in extended source 1st epoch J mag (5.7 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
j_1Class	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	discrete image classification flag in 1st epoch J	smallint	2		-9999	CLASS_MISC
j_1ClassStat	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	N(0,1) stellarness-of-profile statistic in 1st epoch J	real	4		-0.9999995e9	STAT_PROP
j_1Deblend	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	flag indicating parent/child relation in 1st epoch J	int	4		-99999999	CODE_MISC
j_1Ell	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	1-b/a, where a/b=semi-major/minor axes in 1st epoch J	real	4		-0.9999995e9	PHYS_ELLIPTICITY
j_1eNum	lasMergeLog, lasYJHKmergeLog	WSA	the extension number of this 1st epoch J frame	tinyint	1			NUMBER
j_1ErrBits	lasExtendedSource, lasPointSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	processing warning/error bitwise flags in 1st epoch J	int	4		-99999999	CODE_MISC
j_1ErrBits	lasSource	WSA	processing warning/error bitwise flags in 1st epoch J	int	4		-99999999	CODE_MISC
			Apparently not actually an error bit flag, but a count of the number of zero confidence pixels in the default (2 arcsec diameter) aperture.
j_1Eta	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Offset of 1st epoch J detection from master position (+north/-south)	real	4	arcsec	-0.9999995e9	POS_EQ_DEC_OFF
j_1Eta	lasSource	WSA	Offset of 1st epoch J detection from master position (+north/-south)	real	4	arcsec	-0.9999995e9	POS_EQ_DEC_OFF
			When associating individual passband detections into merged sources, a generous (in terms of the positional uncertainties) pairing radius of 2.0 (UKIDSS LAS and GPS; also non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want.
j_1Gausig	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	RMS of axes of ellipse fit in 1st epoch J	real	4	pixels	-0.9999995e9	MORPH_PARAM
j_1HallMag	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Total point source 1st epoch J mag	real	4	mag	-0.9999995e9	PHOT_MAG
j_1HallMagErr	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in total point source 1st epoch J mag	real	4	mag	-0.9999995e9	ERROR
j_1Mag	lasSourceRemeasurement	WSA	1st epoch J mag (as appropriate for this merged source)	real	4	mag	-0.9999995e9	PHOT_MAG
j_1MagErr	lasSourceRemeasurement	WSA	Error in 1st epoch J mag	real	4	mag	-0.9999995e9	ERROR
j_1mfID	lasMergeLog, lasYJHKmergeLog	WSA	the UID of the relevant 1st epoch J multiframe	bigint	8			ID_FRAME
j_1mhExt	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source colour J-H (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
j_1mhExt	lasSource	WSA	Extended source colour J-H (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
j_1mhExtErr	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Error on extended source colour J-H	real	4	mag	-0.9999995e9	ERROR
j_1mhExtErr	lasSource	WSA	Error on extended source colour J-H	real	4	mag	-0.9999995e9	ERROR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
j_1mhPnt	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Point source colour J-H (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
j_1mhPnt	lasSource	WSA	Point source colour J-H (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
j_1mhPntErr	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Error on point source colour J-H	real	4	mag	-0.9999995e9	ERROR
j_1mhPntErr	lasSource	WSA	Error on point source colour J-H	real	4	mag	-0.9999995e9	ERROR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
j_1ObjID	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	the UID of the 1st epoch J detection	bigint	8		-99999999	ID_NUMBER
j_1ObjID	lasSourceRemeasurement	WSA	the UID of the 1st epoch J remeasurement	bigint	8		-99999999	ID_NUMBER
j_1PA	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	ellipse fit celestial orientation in 1st epoch J	real	4	Degrees	-0.9999995e9	POS_POS-ANG
j_1PetroMag	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source 1st epoch J mag (Petrosian)	real	4	mag	-0.9999995e9	PHOT_MAG
j_1PetroMagErr	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in extended source 1st epoch J mag (Petrosian)	real	4	mag	-0.9999995e9	ERROR
j_1ppErrBits	lasExtendedSource, lasPointSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	additional WFAU post-processing error bits in 1st epoch J	int	4		0	CODE_MISC
j_1ppErrBits	lasSource	WSA	additional WFAU post-processing error bits in 1st epoch J	int	4		0	CODE_MISC
			Post-processing error quality bit flags assigned (NB: from UKIDSS DR2 release onwards) in the WSA curation procedure for survey data. From least to most significant byte in the 4-byte integer attribute byte 0 (bits 0 to 7) corresponds to information on generally innocuous conditions that are nonetheless potentially significant as regards the integrity of that detection; byte 1 (bits 8 to 15) corresponds to warnings; byte 2 (bits 16 to 23) corresponds to important warnings; and finally byte 3 (bits 24 to 31) corresponds to severe warnings: Byte Bit Detection quality issue Threshold or bit mask Applies to Decimal Hexadecimal 0 4 Deblended 16 0x00000010 LAS, GCS, GPS, DXS 0 6 Bad pixel(s) in default aperture 64 0x00000040 LAS, GCS, GPS, DXS 2 16 Close to saturated 65536 0x00010000 LAS, GCS, GPS 2 19 Possible crosstalk artefact/contamination 524288 0x00080000 LAS, GCS, DXS 2 22 Lies within a dither offset of the stacked frame boundary 4194304 0x00400000 LAS, GCS, GPS, DXS In this way, the higher the error quality bit flag value, the more likely it is that the detection is spurious. The decimal threshold (column 4) gives the minimum value of the quality flag for a detection having the given condition (since other bits in the flag may be set also; the corresponding hexadecimal value, where each digit corresponds to 4 bits in the flag, can be easier to compute when writing SQL queries to test for a given condition). For example, to exclude all K band sources in the LAS having any error quality condition other than informational ones, include a predicate ... AND kppErrBits ≤ 255. See the SQL Cookbook and other online pages for further information.
j_1PsfMag	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Point source profile-fitted 1st epoch J mag	real	4	mag	-0.9999995e9	PHOT_MAG
j_1PsfMagErr	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in point source profile-fitted 1st epoch J mag	real	4	mag	-0.9999995e9	ERROR
j_1SeqNum	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	the running number of the 1st epoch J detection	int	4		-99999999	ID_NUMBER
j_1SeqNum	lasSourceRemeasurement	WSA	the running number of the 1st epoch J remeasurement	int	4		-99999999	ID_NUMBER
j_1SerMag2D	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source 1st epoch J mag (profile-fitted)	real	4	mag	-0.9999995e9	PHOT_MAG
j_1SerMag2DErr	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in extended source 1st epoch J mag (profile-fitted)	real	4	mag	-0.9999995e9	ERROR
j_1Xi	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Offset of 1st epoch J detection from master position (+east/-west)	real	4	arcsec	-0.9999995e9	POS_EQ_RA_OFF
j_1Xi	lasSource	WSA	Offset of 1st epoch J detection from master position (+east/-west)	real	4	arcsec	-0.9999995e9	POS_EQ_RA_OFF
			When associating individual passband detections into merged sources, a generous (in terms of the positional uncertainties) pairing radius of 2.0 (UKIDSS LAS and GPS; also non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want.
j_2AperMag3	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Default point/extended source 2nd epoch J aperture corrected mag (2.0 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
j_2AperMag3	lasSource	WSA	Default point/extended source 2nd epoch J aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator	real	4	mag	-0.9999995e9	PHOT_MAG
j_2AperMag3Err	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in default point/extended source 2nd epoch J mag (2.0 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
j_2AperMag4	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source 2nd epoch J aperture corrected mag (2.8 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
j_2AperMag4Err	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in extended source 2nd epoch J mag (2.8 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
j_2AperMag6	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source 2nd epoch J aperture corrected mag (5.7 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
j_2AperMag6Err	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in extended source 2nd epoch J mag (5.7 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
j_2Class	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	discrete image classification flag in 2nd epoch J	smallint	2		-9999	CLASS_MISC
j_2ClassStat	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	N(0,1) stellarness-of-profile statistic in 2nd epoch J	real	4		-0.9999995e9	STAT_PROP
j_2Deblend	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	flag indicating parent/child relation in 2nd epoch J	int	4		-99999999	CODE_MISC
j_2Ell	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	1-b/a, where a/b=semi-major/minor axes in 2nd epoch J	real	4		-0.9999995e9	PHYS_ELLIPTICITY
j_2eNum	lasMergeLog, lasYJHKmergeLog	WSA	the extension number of this 2nd epoch J frame	tinyint	1			NUMBER
j_2ErrBits	lasExtendedSource, lasPointSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	processing warning/error bitwise flags in 2nd epoch J	int	4		-99999999	CODE_MISC
j_2ErrBits	lasSource	WSA	processing warning/error bitwise flags in 2nd epoch J	int	4		-99999999	CODE_MISC
			Apparently not actually an error bit flag, but a count of the number of zero confidence pixels in the default (2 arcsec diameter) aperture.
j_2Eta	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Offset of 2nd epoch J detection from master position (+north/-south)	real	4	arcsec	-0.9999995e9	POS_EQ_DEC_OFF
j_2Eta	lasSource	WSA	Offset of 2nd epoch J detection from master position (+north/-south)	real	4	arcsec	-0.9999995e9	POS_EQ_DEC_OFF
			When associating individual passband detections into merged sources, a generous (in terms of the positional uncertainties) pairing radius of 2.0 (UKIDSS LAS and GPS; also non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want.
j_2Gausig	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	RMS of axes of ellipse fit in 2nd epoch J	real	4	pixels	-0.9999995e9	MORPH_PARAM
j_2HallMag	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Total point source 2nd epoch J mag	real	4	mag	-0.9999995e9	PHOT_MAG
j_2HallMagErr	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in total point source 2nd epoch J mag	real	4	mag	-0.9999995e9	ERROR
j_2Mag	lasSourceRemeasurement	WSA	2nd epoch J mag (as appropriate for this merged source)	real	4	mag	-0.9999995e9	PHOT_MAG
j_2MagErr	lasSourceRemeasurement	WSA	Error in 2nd epoch J mag	real	4	mag	-0.9999995e9	ERROR
j_2mfID	lasMergeLog, lasYJHKmergeLog	WSA	the UID of the relevant 2nd epoch J multiframe	bigint	8			ID_FRAME
j_2mrat	twomass_scn	2MASS	J-band average 2nd image moment ratio.	real	4			FIT_PARAM_VALUE
j_2ObjID	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	the UID of the 2nd epoch J detection	bigint	8		-99999999	ID_NUMBER
j_2ObjID	lasSourceRemeasurement	WSA	the UID of the 2nd epoch J remeasurement	bigint	8		-99999999	ID_NUMBER
j_2PA	lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	ellipse fit celestial orientation in 2nd epoch J	real	4	Degrees	-0.9999995e9	POS_POS-ANG
j_2PetroMag	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source 2nd epoch J mag (Petrosian)	real	4	mag	-0.9999995e9	PHOT_MAG
j_2PetroMagErr	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in extended source 2nd epoch J mag (Petrosian)	real	4	mag	-0.9999995e9	ERROR
j_2ppErrBits	lasExtendedSource, lasPointSource, lasSourceRemeasurement, lasYJHKsource, reliableLasPointSource	WSA	additional WFAU post-processing error bits in 2nd epoch J	int	4		0	CODE_MISC
j_2ppErrBits	lasSource	WSA	additional WFAU post-processing error bits in 2nd epoch J	int	4		0	CODE_MISC
			Post-processing error quality bit flags assigned (NB: from UKIDSS DR2 release onwards) in the WSA curation procedure for survey data. From least to most significant byte in the 4-byte integer attribute byte 0 (bits 0 to 7) corresponds to information on generally innocuous conditions that are nonetheless potentially significant as regards the integrity of that detection; byte 1 (bits 8 to 15) corresponds to warnings; byte 2 (bits 16 to 23) corresponds to important warnings; and finally byte 3 (bits 24 to 31) corresponds to severe warnings: Byte Bit Detection quality issue Threshold or bit mask Applies to Decimal Hexadecimal 0 4 Deblended 16 0x00000010 LAS, GCS, GPS, DXS 0 6 Bad pixel(s) in default aperture 64 0x00000040 LAS, GCS, GPS, DXS 2 16 Close to saturated 65536 0x00010000 LAS, GCS, GPS 2 19 Possible crosstalk artefact/contamination 524288 0x00080000 LAS, GCS, DXS 2 22 Lies within a dither offset of the stacked frame boundary 4194304 0x00400000 LAS, GCS, GPS, DXS In this way, the higher the error quality bit flag value, the more likely it is that the detection is spurious. The decimal threshold (column 4) gives the minimum value of the quality flag for a detection having the given condition (since other bits in the flag may be set also; the corresponding hexadecimal value, where each digit corresponds to 4 bits in the flag, can be easier to compute when writing SQL queries to test for a given condition). For example, to exclude all K band sources in the LAS having any error quality condition other than informational ones, include a predicate ... AND kppErrBits ≤ 255. See the SQL Cookbook and other online pages for further information.
j_2PsfMag	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Point source profile-fitted 2nd epoch J mag	real	4	mag	-0.9999995e9	PHOT_MAG
j_2PsfMagErr	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in point source profile-fitted 2nd epoch J mag	real	4	mag	-0.9999995e9	ERROR
j_2SeqNum	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	the running number of the 2nd epoch J detection	int	4		-99999999	ID_NUMBER
j_2SeqNum	lasSourceRemeasurement	WSA	the running number of the 2nd epoch J remeasurement	int	4		-99999999	ID_NUMBER
j_2SerMag2D	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Extended source 2nd epoch J mag (profile-fitted)	real	4	mag	-0.9999995e9	PHOT_MAG
j_2SerMag2DErr	lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableLasPointSource	WSA	Error in extended source 2nd epoch J mag (profile-fitted)	real	4	mag	-0.9999995e9	ERROR
j_2Xi	lasExtendedSource, lasPointSource, lasYJHKsource, reliableLasPointSource	WSA	Offset of 2nd epoch J detection from master position (+east/-west)	real	4	arcsec	-0.9999995e9	POS_EQ_RA_OFF
j_2Xi	lasSource	WSA	Offset of 2nd epoch J detection from master position (+east/-west)	real	4	arcsec	-0.9999995e9	POS_EQ_RA_OFF
			When associating individual passband detections into merged sources, a generous (in terms of the positional uncertainties) pairing radius of 2.0 (UKIDSS LAS and GPS; also non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want.
j_5sig_ba	twomass_xsc	2MASS	J minor/major axis ratio fit to the 5-sigma isophote.	real	4			PHYS_AXIS-RATIO
j_5sig_phi	twomass_xsc	2MASS	J angle to 5-sigma major axis (E of N).	smallint	2	degrees		ERROR
j_5surf	twomass_xsc	2MASS	J central surface brightness (r<=5).	real	4	mag		PHOT_SB_GENERAL
j_ba	twomass_xsc	2MASS	J minor/major axis ratio fit to the 3-sigma isophote.	real	4			PHYS_AXIS-RATIO
j_back	twomass_xsc	2MASS	J coadd median background.	real	4			CODE_MISC
j_bisym_chi	twomass_xsc	2MASS	J bi-symmetric cross-correlation chi.	real	4			FIT_PARAM_VALUE
j_bisym_rat	twomass_xsc	2MASS	J bi-symmetric flux ratio.	real	4			PHOT_FLUX_RATIO
j_bndg_amp	twomass_xsc	2MASS	J banding maximum FT amplitude on this side of coadd.	real	4	DN		FIT_PARAM_VALUE
j_bndg_per	twomass_xsc	2MASS	J banding Fourier Transf. period on this side of coadd.	int	4	arcsec		FIT_PARAM_VALUE
j_chif_ellf	twomass_xsc	2MASS	J % chi-fraction for elliptical fit to 3-sig isophote.	real	4			FIT_PARAM_VALUE
j_cmsig	twomass_psc	2MASS	Corrected photometric uncertainty for the default J-band magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_con_indx	twomass_xsc	2MASS	J concentration index r_75%/r_25%.	real	4			PHYS_CONCENT_INDEX
j_d_area	twomass_xsc	2MASS	J 5-sigma to 3-sigma differential area.	smallint	2			FIT_RESIDUAL
j_flg_10	twomass_xsc	2MASS	J confusion flag for 10 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_15	twomass_xsc	2MASS	J confusion flag for 15 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_20	twomass_xsc	2MASS	J confusion flag for 20 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_25	twomass_xsc	2MASS	J confusion flag for 25 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_30	twomass_xsc	2MASS	J confusion flag for 30 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_40	twomass_xsc	2MASS	J confusion flag for 40 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_5	twomass_xsc	2MASS	J confusion flag for 5 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_50	twomass_xsc	2MASS	J confusion flag for 50 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_60	twomass_xsc	2MASS	J confusion flag for 60 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_7	twomass_xsc	2MASS	J confusion flag for 7 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_70	twomass_xsc	2MASS	J confusion flag for 70 arcsec circular ap. mag.	smallint	2			CODE_MISC
j_flg_c	twomass_xsc	2MASS	J confusion flag for Kron circular mag.	smallint	2			CODE_MISC
j_flg_e	twomass_xsc	2MASS	J confusion flag for Kron elliptical mag.	smallint	2			CODE_MISC
j_flg_fc	twomass_xsc	2MASS	J confusion flag for fiducial Kron circ. mag.	smallint	2			CODE_MISC
j_flg_fe	twomass_xsc	2MASS	J confusion flag for fiducial Kron ell. mag.	smallint	2			CODE_MISC
j_flg_i20c	twomass_xsc	2MASS	J confusion flag for 20mag/sq." iso. circ. mag.	smallint	2			CODE_MISC
j_flg_i20e	twomass_xsc	2MASS	J confusion flag for 20mag/sq." iso. ell. mag.	smallint	2			CODE_MISC
j_flg_i21c	twomass_xsc	2MASS	J confusion flag for 21mag/sq." iso. circ. mag.	smallint	2			CODE_MISC
j_flg_i21e	twomass_xsc	2MASS	J confusion flag for 21mag/sq." iso. ell. mag.	smallint	2			CODE_MISC
j_flg_j21fc	twomass_xsc	2MASS	J confusion flag for 21mag/sq." iso. fid. circ. mag.	smallint	2			CODE_MISC
j_flg_j21fe	twomass_xsc	2MASS	J confusion flag for 21mag/sq." iso. fid. ell. mag.	smallint	2			CODE_MISC
j_flg_k20fc	twomass_xsc	2MASS	J confusion flag for 20mag/sq." iso. fid. circ. mag.	smallint	2			CODE_MISC
j_flg_k20fe	twomass_xsc	2MASS	J confusion flag for 20mag/sq." iso. fid. ell. mag.	smallint	2			CODE_MISC
j_m	twomass_psc	2MASS	Default J-band magnitude	real	4	mag		SPECT_FLUX_VALUE
j_m_10	twomass_xsc	2MASS	J 10 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_15	twomass_xsc	2MASS	J 15 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_20	twomass_xsc	2MASS	J 20 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_25	twomass_xsc	2MASS	J 25 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_30	twomass_xsc	2MASS	J 30 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_40	twomass_xsc	2MASS	J 40 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_5	twomass_xsc	2MASS	J 5 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_50	twomass_xsc	2MASS	J 50 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_60	twomass_xsc	2MASS	J 60 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_7	twomass_xsc	2MASS	J 7 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_70	twomass_xsc	2MASS	J 70 arcsec radius circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_c	twomass_xsc	2MASS	J Kron circular aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_e	twomass_xsc	2MASS	J Kron elliptical aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_ext	twomass_xsc	2MASS	J mag from fit extrapolation.	real	4	mag		SPECT_FLUX_VALUE
j_m_fc	twomass_xsc	2MASS	J fiducial Kron circular magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_fe	twomass_xsc	2MASS	J fiducial Kron ell. mag aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_i20c	twomass_xsc	2MASS	J 20mag/sq." isophotal circular ap. magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_i20e	twomass_xsc	2MASS	J 20mag/sq." isophotal elliptical ap. magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_i21c	twomass_xsc	2MASS	J 21mag/sq." isophotal circular ap. magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_i21e	twomass_xsc	2MASS	J 21mag/sq." isophotal elliptical ap. magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_j21fc	twomass_xsc	2MASS	J 21mag/sq." isophotal fiducial circ. ap. mag.	real	4	mag		SPECT_FLUX_VALUE
j_m_j21fe	twomass_xsc	2MASS	J 21mag/sq." isophotal fiducial ell. ap. magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_k20fc	twomass_xsc	2MASS	J 20mag/sq." isophotal fiducial circ. ap. mag.	real	4	mag		SPECT_FLUX_VALUE
j_m_k20fe	twomass_xsc	2MASS	J 20mag/sq." isophotal fiducial ell. ap. magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_stdap	twomass_psc	2MASS	J-band "standard" aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_m_sys	twomass_xsc	2MASS	J system photometry magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_mnsurfb_eff	twomass_xsc	2MASS	J mean surface brightness at the half-light radius.	real	4	mag		PHOT_SB_GENERAL
j_msig_10	twomass_xsc	2MASS	J 1-sigma uncertainty in 10 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_15	twomass_xsc	2MASS	J 1-sigma uncertainty in 15 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_20	twomass_xsc	2MASS	J 1-sigma uncertainty in 20 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_25	twomass_xsc	2MASS	J 1-sigma uncertainty in 25 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_30	twomass_xsc	2MASS	J 1-sigma uncertainty in 30 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_40	twomass_xsc	2MASS	J 1-sigma uncertainty in 40 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_5	twomass_xsc	2MASS	J 1-sigma uncertainty in 5 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_50	twomass_xsc	2MASS	J 1-sigma uncertainty in 50 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_60	twomass_xsc	2MASS	J 1-sigma uncertainty in 60 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_7	twomass_xsc	2MASS	J 1-sigma uncertainty in 7 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_70	twomass_xsc	2MASS	J 1-sigma uncertainty in 70 arcsec circular ap. mag.	real	4	mag		ERROR
j_msig_c	twomass_xsc	2MASS	J 1-sigma uncertainty in Kron circular mag.	real	4	mag		ERROR
j_msig_e	twomass_xsc	2MASS	J 1-sigma uncertainty in Kron elliptical mag.	real	4	mag		ERROR
j_msig_ext	twomass_xsc	2MASS	J 1-sigma uncertainty in mag from fit extrapolation.	real	4	mag		ERROR
j_msig_fc	twomass_xsc	2MASS	J 1-sigma uncertainty in fiducial Kron circ. mag.	real	4	mag		ERROR
j_msig_fe	twomass_xsc	2MASS	J 1-sigma uncertainty in fiducial Kron ell. mag.	real	4	mag		ERROR
j_msig_i20c	twomass_xsc	2MASS	J 1-sigma uncertainty in 20mag/sq." iso. circ. mag.	real	4	mag		ERROR
j_msig_i20e	twomass_xsc	2MASS	J 1-sigma uncertainty in 20mag/sq." iso. ell. mag.	real	4	mag		ERROR
j_msig_i21c	twomass_xsc	2MASS	J 1-sigma uncertainty in 21mag/sq." iso. circ. mag.	real	4	mag		ERROR
j_msig_i21e	twomass_xsc	2MASS	J 1-sigma uncertainty in 21mag/sq." iso. ell. mag.	real	4	mag		ERROR
j_msig_j21fc	twomass_xsc	2MASS	J 1-sigma uncertainty in 21mag/sq." iso.fid.circ.mag.	real	4	mag		ERROR
j_msig_j21fe	twomass_xsc	2MASS	J 1-sigma uncertainty in 21mag/sq." iso.fid.ell.mag.	real	4	mag		ERROR
j_msig_k20fc	twomass_xsc	2MASS	J 1-sigma uncertainty in 20mag/sq." iso.fid.circ. mag.	real	4	mag		ERROR
j_msig_k20fe	twomass_xsc	2MASS	J 1-sigma uncertainty in 20mag/sq." iso.fid.ell.mag.	real	4	mag		ERROR
j_msig_stdap	twomass_psc	2MASS	Uncertainty in the J-band standard aperture magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_msig_sys	twomass_xsc	2MASS	J 1-sigma uncertainty in system photometry mag.	real	4	mag		ERROR
j_msigcom	twomass_psc	2MASS	Combined, or total photometric uncertainty for the default J-band magnitude.	real	4	mag		SPECT_FLUX_VALUE
j_msnr10	twomass_scn	2MASS	The estimated J-band magnitude at which SNR=10 is achieved for this scan.	real	4	mag		SPECT_FLUX_VALUE
j_n_snr10	twomass_scn	2MASS	Number of point sources at J-band with SNR>10 (instrumental mag <=15.8)	int	4			NUMBER
j_pchi	twomass_xsc	2MASS	J chi^2 of fit to rad. profile (LCSB: alpha scale len).	real	4			FIT_PARAM_VALUE
j_peak	twomass_xsc	2MASS	J peak pixel brightness.	real	4	mag		PHOT_SB_GENERAL
j_perc_darea	twomass_xsc	2MASS	J 5-sigma to 3-sigma percent area change.	smallint	2			FIT_PARAM
j_phi	twomass_xsc	2MASS	J angle to 3-sigma major axis (E of N).	smallint	2	degrees		POS_POS-ANG
j_psfchi	twomass_psc	2MASS	Reduced chi-squared goodness-of-fit value for the J-band profile-fit photometry made on the 1.3 s "Read_2" exposures.	real	4			FIT_PARAM_VALUE
j_psp	twomass_scn	2MASS	J-band photometric sensitivity paramater (PSP).	real	4			INST_SENSITIVITY
j_pts_noise	twomass_scn	2MASS	Base-10 logarithm of the mode of the noise distribution for all point source detections in the scan, where the noise is estimated from the measured J-band photometric errors and is expressed in units of mJy.	real	4			INST_NOISE
j_r_c	twomass_xsc	2MASS	J Kron circular aperture radius.	real	4	arcsec		EXTENSION_RAD
j_r_e	twomass_xsc	2MASS	J Kron elliptical aperture semi-major axis.	real	4	arcsec		EXTENSION_RAD
j_r_eff	twomass_xsc	2MASS	J half-light (integrated half-flux point) radius.	real	4	arcsec		EXTENSION_RAD
j_r_i20c	twomass_xsc	2MASS	J 20mag/sq." isophotal circular aperture radius.	real	4	arcsec		EXTENSION_RAD
j_r_i20e	twomass_xsc	2MASS	J 20mag/sq." isophotal elliptical ap. semi-major axis.	real	4	arcsec		EXTENSION_RAD
j_r_i21c	twomass_xsc	2MASS	J 21mag/sq." isophotal circular aperture radius.	real	4	arcsec		EXTENSION_RAD
j_r_i21e	twomass_xsc	2MASS	J 21mag/sq." isophotal elliptical ap. semi-major axis.	real	4	arcsec		EXTENSION_RAD
j_resid_ann	twomass_xsc	2MASS	J residual annulus background median.	real	4	DN		CODE_MISC
j_sc_1mm	twomass_xsc	2MASS	J 1st moment (score) (LCSB: super blk 2,4,8 SNR).	real	4			CODE_MISC
j_sc_2mm	twomass_xsc	2MASS	J 2nd moment (score) (LCSB: SNRMAX - super SNR max).	real	4			CODE_MISC
j_sc_msh	twomass_xsc	2MASS	J median shape score.	real	4			CODE_MISC
j_sc_mxdn	twomass_xsc	2MASS	J mxdn (score) (LCSB: BSNR - block/smoothed SNR).	real	4			CODE_MISC
j_sc_r1	twomass_xsc	2MASS	J r1 (score).	real	4			CODE_MISC
j_sc_r23	twomass_xsc	2MASS	J r23 (score) (LCSB: TSNR - integrated SNR for r=15).	real	4			CODE_MISC
j_sc_sh	twomass_xsc	2MASS	J shape (score).	real	4			CODE_MISC
j_sc_vint	twomass_xsc	2MASS	J vint (score).	real	4			CODE_MISC
j_sc_wsh	twomass_xsc	2MASS	J wsh (score) (LCSB: PSNR - peak raw SNR).	real	4			CODE_MISC
j_seetrack	twomass_xsc	2MASS	J band seetracking score.	real	4			CODE_MISC
j_sh0	twomass_xsc	2MASS	J ridge shape (LCSB: BSNR limit).	real	4			FIT_PARAM
j_shape_avg	twomass_scn	2MASS	J-band average seeing shape for scan.	real	4			INST_SEEING
j_shape_rms	twomass_scn	2MASS	RMS-error of J-band average seeing shape.	real	4			INST_SEEING
j_sig_sh0	twomass_xsc	2MASS	J ridge shape sigma (LCSB: B2SNR limit).	real	4			FIT_PARAM
j_snr	twomass_psc	2MASS	J-band "scan" signal-to-noise ratio.	real	4	mag		INST_NOISE
j_subst2	twomass_xsc	2MASS	J residual background #2 (score).	real	4			CODE_MISC
j_zp_ap	twomass_scn	2MASS	Photometric zero-point for J-band aperture photometry.	real	4	mag		PHOT_ZP
jAperMag1	gpsJHKsource, gpsPointSource, reliableGpsPointSource	WSA	Extended source J aperture corrected mag (0.7 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag1	gpsSource	WSA	Extended source J aperture corrected mag (0.7 arcsec aperture diameter) If in doubt use this flux estimator	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag1Err	gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource	WSA	Error in extended source J mag (1.4 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
jAperMag3	dxsJKsource, gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource	WSA	Default point/extended source J aperture corrected mag (2.0 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag3	dxsSource, gcsSource, gpsSource	WSA	Default point/extended source J aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag3	reliableUdsSource	WSA	Default point/extended source J mag, no aperture correction applied	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag3	udsSource	WSA	Default point/extended source J mag, no aperture correction applied If in doubt use this flux estimator	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag3Err	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource	WSA	Error in default point/extended source J mag (2.0 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
jAperMag4	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource	WSA	Extended source J aperture corrected mag (2.8 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag4	reliableUdsSource, udsSource	WSA	Extended source J mag, no aperture correction applied	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag4Err	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource	WSA	Error in extended source J mag (2.8 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
jAperMag6	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource	WSA	Extended source J aperture corrected mag (5.7 arcsec aperture diameter)	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag6	reliableUdsSource, udsSource	WSA	Extended source J mag, no aperture correction applied	real	4	mag	-0.9999995e9	PHOT_MAG
jAperMag6Err	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource, reliableUdsSource, udsSource	WSA	Error in extended source J mag (5.7 arcsec aperture diameter)	real	4	mag	-0.9999995e9	ERROR
jClass	dxsJKsource, dxsSource, dxsSourceRemeasurement, gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource, udsSourceRemeasurement	WSA	discrete image classification flag in J	smallint	2		-9999	CLASS_MISC
jClassStat	dxsJKsource, dxsSource, dxsSourceRemeasurement, gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsSourceRemeasurement, reliableDxsSource, reliableGcsPointSource, udsSourceRemeasurement	WSA	N(0,1) stellarness-of-profile statistic in J	real	4		-0.9999995e9	STAT_PROP
jClassStat	gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource, reliableUdsSource, udsSource	WSA	S-Extractor classification statistic in J	real	4		-0.9999995e9	STAT_PROP
jdate	twomass_psc	2MASS	The Julian Date of the source measurement accurate to +-30 seconds.	float	8	Julian days		TIME_DATE
jdate	twomass_scn	2MASS	Julian Date at beginning of scan.	float	8	Julian days		TIME_DATE
jdate	twomass_xsc	2MASS	Julian date of the source measurement accurate to +-3 minutes.	float	8	Julian days		TIME_DATE
jDeblend	dxsJKsource, dxsSource, dxsSourceRemeasurement, gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource, udsSourceRemeasurement	WSA	flag indicating parent/child relation in J	int	4		-99999999	CODE_MISC
jEll	dxsJKsource, dxsSource, dxsSourceRemeasurement, gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource, udsSourceRemeasurement	WSA	1-b/a, where a/b=semi-major/minor axes in J	real	4		-0.9999995e9	PHYS_ELLIPTICITY
jeNum	dxsJKmergeLog, gpsJHKmergeLog	WSA	the extension number of this frame	tinyint	1			NUMBER
jeNum	dxsMergeLog, gcsMergeLog, gcsZYJHKmergeLog, gpsMergeLog, udsMergeLog	WSA	the extension number of this J frame	tinyint	1			NUMBER
jErrBits	dxsJKsource, dxsSourceRemeasurement, gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSourceRemeasurement, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSourceRemeasurement	WSA	processing warning/error bitwise flags in J	int	4		-99999999	CODE_MISC
jErrBits	dxsSource, gcsSource	WSA	processing warning/error bitwise flags in J	int	4		-99999999	CODE_MISC
			Apparently not actually an error bit flag, but a count of the number of zero confidence pixels in the default (2 arcsec diameter) aperture.
jErrBits	gpsSource, udsSource	WSA	processing warning/error bitwise flags in J	int	4		-99999999	CODE_MISC
			This uses the FLAGS attribute in SE. The individual bit flags that this can be decomposed into are as follows: Bit Flag Meaning 1 The object has neighbours, bright enough and close enough to significantly bias the MAG_AUTO photometry or bad pixels (more than 10% of photometry affected). 2 The object was originally blended with another 4 At least one pixel is saturated (or very close to) 8 The object is truncated (too close to an image boundary) 16 Object's aperture data are incomplete or corrupted 32 Object's isophotal data are imcomplete or corrupted. This is an old flag inherited from SE v1.0, and is kept for compatability reasons. It doesn't have any consequence for the extracted parameters. 64 Memory overflow occurred during deblending 128 Memory overflow occurred during extraction
jEta	dxsJKsource, gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource	WSA	Offset of J detection from master position (+north/-south)	real	4	arcsec	-0.9999995e9	POS_EQ_DEC_OFF
jEta	dxsSource, gcsSource, gpsSource, udsSource	WSA	Offset of J detection from master position (+north/-south)	real	4	arcsec	-0.9999995e9	POS_EQ_DEC_OFF
			When associating individual passband detections into merged sources, a generous (in terms of the positional uncertainties) pairing radius of 2.0 (UKIDSS LAS and GPS; also non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want.
jGausig	dxsJKsource, dxsSource, dxsSourceRemeasurement, gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource, udsSourceRemeasurement	WSA	RMS of axes of ellipse fit in J	real	4	pixels	-0.9999995e9	MORPH_PARAM
jHallMag	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource	WSA	Total point source J mag	real	4	mag	-0.9999995e9	PHOT_MAG
jHallMag	reliableUdsSource, udsSource	WSA	Not available in SE output	real	4	mag	-0.9999995e9	PHOT_MAG
jHallMagErr	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource	WSA	Error in total point source J mag	real	4	mag	-0.9999995e9	ERROR
jHallMagErr	reliableUdsSource, udsSource	WSA	Not available in SE output	real	4	mag	-0.9999995e9	ERROR
jitterID	Multiframe	WSA	Serial number in this telescope jitter pattern {image primary HDU keyword: JITTER_I}	smallint	2		-9999	ID_NUMBER
jitterID	Multiframe	WSATransit	Serial number in this telescope jitter pattern {image primary HDU keyword: JITTER_I}	smallint	2		-9999	ID_NUMBER
jitterX	Multiframe	WSA	X (RA) offset in tel jitter pattern {image primary HDU keyword: JITTER_X}	real	4	arcsec	-0.9999995e9	POS_EQ_RA_OFF
jitterX	Multiframe	WSATransit	X (RA) offset in tel jitter pattern {image primary HDU keyword: JITTER_X}	real	4	arcsec	-0.9999995e9	POS_EQ_RA_OFF
jitterY	Multiframe	WSA	Y (Dec) offset in tel jitter pattern {image primary HDU keyword: JITTER_Y}	real	4	arcsec	-0.9999995e9	POS_EQ_DEC_OFF
jitterY	Multiframe	WSATransit	Y (Dec) offset in tel jitter pattern {image primary HDU keyword: JITTER_Y}	real	4	arcsec	-0.9999995e9	POS_EQ_DEC_OFF
jMag	CurrentStdStarInfo, PreviousStdStarInfo	WSA	J band total magnitude of star (from external sources if primary)	real	4	mag		PHOT_INT-MAG
jMag	dxsSourceRemeasurement, gcsSourceRemeasurement, gpsSourceRemeasurement, udsSourceRemeasurement	WSA	J mag (as appropriate for this merged source)	real	4	mag	-0.9999995e9	PHOT_MAG
jMag	ukirtFSstars	WSA	J band total magnitude on the MKO(UFTI) system	real	4	mag		PHOT_INT-MAG
jMagErr	CurrentStdStarInfo, PreviousStdStarInfo	WSA	J band magnitude error of star	real	4	mag		ERROR
jMagErr	dxsSourceRemeasurement, gcsSourceRemeasurement, gpsSourceRemeasurement, udsSourceRemeasurement	WSA	Error in J mag	real	4	mag	-0.9999995e9	ERROR
jMagErr	ukirtFSstars	WSA	J band magnitude error	real	4	mag		ERROR
jmfID	dxsJKmergeLog, gpsJHKmergeLog	WSA	the UID of the relevant multiframe	bigint	8			ID_FRAME
jmfID	dxsMergeLog, gcsMergeLog, gcsZYJHKmergeLog, gpsMergeLog, udsMergeLog	WSA	the UID of the relevant J multiframe	bigint	8			ID_FRAME
jmh	dxsSourceRemeasurement, gcsSourceRemeasurement, gpsSourceRemeasurement, lasSourceRemeasurement, udsSourceRemeasurement	WSA	Default colour J-H (using appropriate mags)	real	4	mag		PHOT_COLOR
jmhErr	dxsSourceRemeasurement, gcsSourceRemeasurement, gpsSourceRemeasurement, lasSourceRemeasurement, udsSourceRemeasurement	WSA	Error on colour J-H	real	4	mag		ERROR
jmhExt	dxsJKsource, gcsPointSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource, reliableUdsSource	WSA	Extended source colour J-H (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
jmhExt	dxsSource, gcsSource, udsSource	WSA	Extended source colour J-H (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
jmhExtErr	dxsJKsource, gcsPointSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource, reliableUdsSource	WSA	Error on extended source colour J-H	real	4	mag	-0.9999995e9	ERROR
jmhExtErr	dxsSource, gcsSource, udsSource	WSA	Error on extended source colour J-H	real	4	mag	-0.9999995e9	ERROR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
jmhPnt	dxsJKsource, gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource	WSA	Point source colour J-H (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
jmhPnt	dxsSource, gcsSource, gpsSource, udsSource	WSA	Point source colour J-H (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
jmhPntErr	dxsJKsource, gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource	WSA	Error on point source colour J-H	real	4	mag	-0.9999995e9	ERROR
jmhPntErr	dxsSource, gcsSource, gpsSource, udsSource	WSA	Error on point source colour J-H	real	4	mag	-0.9999995e9	ERROR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
jmkExt	dxsJKsource, reliableDxsSource, reliableUdsSource	WSA	Extended source colour J-K (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
jmkExt	dxsSource, udsSource	WSA	Extended source colour J-K (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
jmkExtErr	dxsJKsource, reliableDxsSource, reliableUdsSource	WSA	Error on extended source colour J-K	real	4	mag	-0.9999995e9	ERROR
jmkExtErr	dxsSource, udsSource	WSA	Error on extended source colour J-K	real	4	mag	-0.9999995e9	ERROR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
jmkPnt	dxsJKsource, reliableDxsSource, reliableUdsSource	WSA	Point source colour J-K (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
jmkPnt	dxsSource, udsSource	WSA	Point source colour J-K (using aperMag3)	real	4	mag	-0.9999995e9	PHOT_COLOR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
jmkPntErr	dxsJKsource, reliableDxsSource, reliableUdsSource	WSA	Error on point source colour J-K	real	4	mag	-0.9999995e9	ERROR
jmkPntErr	dxsSource, udsSource	WSA	Error on point source colour J-K	real	4	mag	-0.9999995e9	ERROR
			Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
jObjID	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource	WSA	the UID of the J detection	bigint	8		-99999999	ID_NUMBER
jObjID	dxsSourceRemeasurement, gcsSourceRemeasurement, gpsSourceRemeasurement, udsSourceRemeasurement	WSA	the UID of the J remeasurement	bigint	8		-99999999	ID_NUMBER
joinCriterion	RequiredNeighbours	WSA	the join criterion (search radius for matches)	real	4	arcminutes		??
joinCriterion	RequiredNeighbours	WSATransit	the join criterion (search radius for matches)	real	4	arcminutes		??
jPA	dxsJKsource, dxsSource, dxsSourceRemeasurement, gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource, udsSourceRemeasurement	WSA	ellipse fit celestial orientation in J	real	4	Degrees	-0.9999995e9	POS_POS-ANG
jPetroMag	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource, reliableUdsSource, udsSource	WSA	Extended source J mag (Petrosian)	real	4	mag	-0.9999995e9	PHOT_MAG
jPetroMagErr	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource, reliableUdsSource, udsSource	WSA	Error in extended source J mag (Petrosian)	real	4	mag	-0.9999995e9	ERROR
jppErrBits	dxsJKsource, dxsSourceRemeasurement, gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource, udsSourceRemeasurement	WSA	additional WFAU post-processing error bits in J	int	4		0	CODE_MISC
jppErrBits	dxsSource, gcsSource	WSA	additional WFAU post-processing error bits in J	int	4		0	CODE_MISC
			Post-processing error quality bit flags assigned (NB: from UKIDSS DR2 release onwards) in the WSA curation procedure for survey data. From least to most significant byte in the 4-byte integer attribute byte 0 (bits 0 to 7) corresponds to information on generally innocuous conditions that are nonetheless potentially significant as regards the integrity of that detection; byte 1 (bits 8 to 15) corresponds to warnings; byte 2 (bits 16 to 23) corresponds to important warnings; and finally byte 3 (bits 24 to 31) corresponds to severe warnings: Byte Bit Detection quality issue Threshold or bit mask Applies to Decimal Hexadecimal 0 4 Deblended 16 0x00000010 LAS, GCS, GPS, DXS 0 6 Bad pixel(s) in default aperture 64 0x00000040 LAS, GCS, GPS, DXS 2 16 Close to saturated 65536 0x00010000 LAS, GCS, GPS 2 19 Possible crosstalk artefact/contamination 524288 0x00080000 LAS, GCS, DXS 2 22 Lies within a dither offset of the stacked frame boundary 4194304 0x00400000 LAS, GCS, GPS, DXS In this way, the higher the error quality bit flag value, the more likely it is that the detection is spurious. The decimal threshold (column 4) gives the minimum value of the quality flag for a detection having the given condition (since other bits in the flag may be set also; the corresponding hexadecimal value, where each digit corresponds to 4 bits in the flag, can be easier to compute when writing SQL queries to test for a given condition). For example, to exclude all K band sources in the LAS having any error quality condition other than informational ones, include a predicate ... AND kppErrBits ≤ 255. See the SQL Cookbook and other online pages for further information.
jPsfMag	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource	WSA	Point source profile-fitted J mag	real	4	mag	-0.9999995e9	PHOT_MAG
jPsfMag	reliableUdsSource, udsSource	WSA	Not available in SE output	real	4	mag	-0.9999995e9	PHOT_MAG
jPsfMagErr	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource	WSA	Error in point source profile-fitted J mag	real	4	mag	-0.9999995e9	ERROR
jPsfMagErr	reliableUdsSource, udsSource	WSA	Not available in SE output	real	4	mag	-0.9999995e9	ERROR
jSeqNum	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource, udsSource	WSA	the running number of the J detection	int	4		-99999999	ID_NUMBER
jSeqNum	dxsSourceRemeasurement, gcsSourceRemeasurement, gpsSourceRemeasurement, udsSourceRemeasurement	WSA	the running number of the J remeasurement	int	4		-99999999	ID_NUMBER
jSerMag2D	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource	WSA	Extended source J mag (profile-fitted)	real	4	mag	-0.9999995e9	PHOT_MAG
jSerMag2D	reliableUdsSource, udsSource	WSA	Not available in SE output	real	4	mag	-0.9999995e9	PHOT_MAG
jSerMag2DErr	dxsJKsource, dxsSource, gcsPointSource, gcsSource, gcsZYJHKsource, reliableDxsSource, reliableGcsPointSource	WSA	Error in extended source J mag (profile-fitted)	real	4	mag	-0.9999995e9	ERROR
jSerMag2DErr	reliableUdsSource, udsSource	WSA	Not available in SE output	real	4	mag	-0.9999995e9	ERROR
julianDayNum	CurrentNightlyExt	WSATransit	the Julian Day number of the UKIRT night {image primary HDU keyword: UTDATE}	int	4	Julian days		TIME_DATE
julianDayNum	CurrentNightlyExt, DetectorSetUp, MultiframeDetector, MultiframeSetUp, PreviousNightlyExt	WSA	the Julian Day number of the UKIRT night {image primary HDU keyword: UTDATE}	int	4	Julian days		TIME_DATE
julianDayNum	Multiframe	WSA	the Julian Day number of the UKIRT night	int	4	Julian days		TIME_DATE
julianDayNum	Multiframe	WSATransit	the Julian Day number of the UKIRT night	int	4	Julian days		TIME_DATE
junkSource	JunkDetection	SSA	Source of junk: 1=satellite track; 2=diffraction spike; 3=bright stellar halo	tinyint	1			CLASS_CODE
jXi	dxsJKsource, gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableDxsSource, reliableGcsPointSource, reliableGpsPointSource, reliableUdsSource	WSA	Offset of J detection from master position (+east/-west)	real	4	arcsec	-0.9999995e9	POS_EQ_RA_OFF
jXi	dxsSource, gcsSource, gpsSource, udsSource	WSA	Offset of J detection from master position (+east/-west)	real	4	arcsec	-0.9999995e9	POS_EQ_RA_OFF
			When associating individual passband detections into merged sources, a generous (in terms of the positional uncertainties) pairing radius of 2.0 (UKIDSS LAS and GPS; also non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want.