WFCAM Science Archive

Glossary of WSA attributes

This Glossary alphabetically lists all attributes used in the UKIDSSDR2 database(s) held in the WSA. If you would like to have more information about the schema tables please use the UKIDSSDR2 Schema Browser (other Browser versions).

A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z

K

Name Schema Table Database Description Type Length Unit Default Value Unified Content Descriptor

k_1AperMag3 gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableGcsPointSource, reliableGpsPointSource WSA Default point/extended source 1st epoch K aperture corrected mag (2.0 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_1AperMag3 gcsSource, gpsSource WSA Default point/extended source 1st epoch K aperture corrected mag (2.0 arcsec aperture diameter)
If in doubt use this flux estimator real 4 mag -0.9999995e9 PHOT_MAG

k_1AperMag3Err gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in default point/extended source 1st epoch K mag (2.0 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_1AperMag4 gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Extended source 1st epoch K aperture corrected mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_1AperMag4Err gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in extended source 1st epoch K mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_1AperMag6 gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Extended source 1st epoch K aperture corrected mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_1AperMag6Err gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in extended source 1st epoch K mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_1Class gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA discrete image classification flag in 1st epoch K smallint 2 -9999 CLASS_MISC

k_1ClassStat gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA N(0,1) stellarness-of-profile statistic in 1st epoch K real 4 -0.9999995e9 STAT_PROP

k_1Deblend gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA flag indicating parent/child relation in 1st epoch K int 4 -99999999 CODE_MISC

k_1Ell gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA 1-b/a, where a/b=semi-major/minor axes in 1st epoch K real 4 -0.9999995e9 PHYS_ELLIPTICITY

k_1eNum gcsMergeLog, gcsZYJHKmergeLog, gpsJHKmergeLog, gpsMergeLog WSA the extension number of this 1st epoch K frame tinyint 1 NUMBER

k_1ErrBits gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA processing warning/error bitwise flags in 1st epoch K int 4 -99999999 CODE_MISC

k_1ErrBits gcsSource, gpsSource WSA processing warning/error bitwise flags in 1st epoch K 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.

k_1Eta gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableGcsPointSource, reliableGpsPointSource WSA Offset of 1st epoch K detection from master position (+north/-south) real 4 arcsec -0.9999995e9 POS_EQ_DEC_OFF

k_1Eta gcsSource, gpsSource WSA Offset of 1st epoch K 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.

k_1Gausig gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA RMS of axes of ellipse fit in 1st epoch K real 4 pixels -0.9999995e9 MORPH_PARAM

k_1HallMag gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Total point source 1st epoch K mag real 4 mag -0.9999995e9 PHOT_MAG

k_1HallMagErr gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in total point source 1st epoch K mag real 4 mag -0.9999995e9 ERROR

k_1Mag gcsSourceRemeasurement, gpsSourceRemeasurement WSA 1st epoch K mag (as appropriate for this merged source) real 4 mag -0.9999995e9 PHOT_MAG

k_1MagErr gcsSourceRemeasurement, gpsSourceRemeasurement WSA Error in 1st epoch K mag real 4 mag -0.9999995e9 ERROR

k_1mfID gcsMergeLog, gcsZYJHKmergeLog, gpsJHKmergeLog, gpsMergeLog WSA the UID of the relevant 1st epoch K multiframe bigint 8 ID_FRAME

k_1ObjID gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA the UID of the 1st epoch K detection bigint 8 -99999999 ID_NUMBER

k_1ObjID gcsSourceRemeasurement, gpsSourceRemeasurement WSA the UID of the 1st epoch K remeasurement bigint 8 -99999999 ID_NUMBER

k_1PA gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA ellipse fit celestial orientation in 1st epoch K real 4 Degrees -0.9999995e9 POS_POS-ANG

k_1PetroMag gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Extended source 1st epoch K mag (Petrosian) real 4 mag -0.9999995e9 PHOT_MAG

k_1PetroMagErr gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in extended source 1st epoch K mag (Petrosian) real 4 mag -0.9999995e9 ERROR

k_1ppErrBits gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA additional WFAU post-processing error bits in 1st epoch K int 4 0 CODE_MISC

k_1ppErrBits gcsSource, gpsSource WSA additional WFAU post-processing error bits in 1st epoch K 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.

k_1PsfMag gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Point source profile-fitted 1st epoch K mag real 4 mag -0.9999995e9 PHOT_MAG

k_1PsfMagErr gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in point source profile-fitted 1st epoch K mag real 4 mag -0.9999995e9 ERROR

k_1SeqNum gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA the running number of the 1st epoch K detection int 4 -99999999 ID_NUMBER

k_1SeqNum gcsSourceRemeasurement, gpsSourceRemeasurement WSA the running number of the 1st epoch K remeasurement int 4 -99999999 ID_NUMBER

k_1SerMag2D gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Extended source 1st epoch K mag (profile-fitted) real 4 mag -0.9999995e9 PHOT_MAG

k_1SerMag2DErr gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in extended source 1st epoch K mag (profile-fitted) real 4 mag -0.9999995e9 ERROR

k_1Xi gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableGcsPointSource, reliableGpsPointSource WSA Offset of 1st epoch K detection from master position (+east/-west) real 4 arcsec -0.9999995e9 POS_EQ_RA_OFF

k_1Xi gcsSource, gpsSource WSA Offset of 1st epoch K 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.

k_2AperMag3 gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableGcsPointSource, reliableGpsPointSource WSA Default point/extended source 2nd epoch K aperture corrected mag (2.0 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_2AperMag3 gcsSource, gpsSource WSA Default point/extended source 2nd epoch K aperture corrected mag (2.0 arcsec aperture diameter)
If in doubt use this flux estimator real 4 mag -0.9999995e9 PHOT_MAG

k_2AperMag3Err gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in default point/extended source 2nd epoch K mag (2.0 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_2AperMag4 gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Extended source 2nd epoch K aperture corrected mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_2AperMag4Err gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in extended source 2nd epoch K mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_2AperMag6 gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Extended source 2nd epoch K aperture corrected mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_2AperMag6Err gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in extended source 2nd epoch K mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_2Class gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA discrete image classification flag in 2nd epoch K smallint 2 -9999 CLASS_MISC

k_2ClassStat gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA N(0,1) stellarness-of-profile statistic in 2nd epoch K real 4 -0.9999995e9 STAT_PROP

k_2Deblend gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA flag indicating parent/child relation in 2nd epoch K int 4 -99999999 CODE_MISC

k_2Ell gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA 1-b/a, where a/b=semi-major/minor axes in 2nd epoch K real 4 -0.9999995e9 PHYS_ELLIPTICITY

k_2eNum gcsMergeLog, gcsZYJHKmergeLog, gpsJHKmergeLog, gpsMergeLog WSA the extension number of this 2nd epoch K frame tinyint 1 NUMBER

k_2ErrBits gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA processing warning/error bitwise flags in 2nd epoch K int 4 -99999999 CODE_MISC

k_2ErrBits gcsSource, gpsSource WSA processing warning/error bitwise flags in 2nd epoch K 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.

k_2Eta gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableGcsPointSource, reliableGpsPointSource WSA Offset of 2nd epoch K detection from master position (+north/-south) real 4 arcsec -0.9999995e9 POS_EQ_DEC_OFF

k_2Eta gcsSource, gpsSource WSA Offset of 2nd epoch K 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.

k_2Gausig gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA RMS of axes of ellipse fit in 2nd epoch K real 4 pixels -0.9999995e9 MORPH_PARAM

k_2HallMag gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Total point source 2nd epoch K mag real 4 mag -0.9999995e9 PHOT_MAG

k_2HallMagErr gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in total point source 2nd epoch K mag real 4 mag -0.9999995e9 ERROR

k_2Mag gcsSourceRemeasurement, gpsSourceRemeasurement WSA 2nd epoch K mag (as appropriate for this merged source) real 4 mag -0.9999995e9 PHOT_MAG

k_2MagErr gcsSourceRemeasurement, gpsSourceRemeasurement WSA Error in 2nd epoch K mag real 4 mag -0.9999995e9 ERROR

k_2mfID gcsMergeLog, gcsZYJHKmergeLog, gpsJHKmergeLog, gpsMergeLog WSA the UID of the relevant 2nd epoch K multiframe bigint 8 ID_FRAME

k_2mrat twomass_scn 2MASS Ks-band average 2nd image moment ratio. real 4 FIT_PARAM_VALUE

k_2ObjID gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA the UID of the 2nd epoch K detection bigint 8 -99999999 ID_NUMBER

k_2ObjID gcsSourceRemeasurement, gpsSourceRemeasurement WSA the UID of the 2nd epoch K remeasurement bigint 8 -99999999 ID_NUMBER

k_2PA gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA ellipse fit celestial orientation in 2nd epoch K real 4 Degrees -0.9999995e9 POS_POS-ANG

k_2PetroMag gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Extended source 2nd epoch K mag (Petrosian) real 4 mag -0.9999995e9 PHOT_MAG

k_2PetroMagErr gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in extended source 2nd epoch K mag (Petrosian) real 4 mag -0.9999995e9 ERROR

k_2ppErrBits gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSourceRemeasurement, reliableGcsPointSource, reliableGpsPointSource WSA additional WFAU post-processing error bits in 2nd epoch K int 4 0 CODE_MISC

k_2ppErrBits gcsSource, gpsSource WSA additional WFAU post-processing error bits in 2nd epoch K 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.

k_2PsfMag gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Point source profile-fitted 2nd epoch K mag real 4 mag -0.9999995e9 PHOT_MAG

k_2PsfMagErr gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in point source profile-fitted 2nd epoch K mag real 4 mag -0.9999995e9 ERROR

k_2SeqNum gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA the running number of the 2nd epoch K detection int 4 -99999999 ID_NUMBER

k_2SeqNum gcsSourceRemeasurement, gpsSourceRemeasurement WSA the running number of the 2nd epoch K remeasurement int 4 -99999999 ID_NUMBER

k_2SerMag2D gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Extended source 2nd epoch K mag (profile-fitted) real 4 mag -0.9999995e9 PHOT_MAG

k_2SerMag2DErr gcsPointSource, gcsSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, gpsSource, reliableGcsPointSource, reliableGpsPointSource WSA Error in extended source 2nd epoch K mag (profile-fitted) real 4 mag -0.9999995e9 ERROR

k_2Xi gcsPointSource, gcsZYJHKsource, gpsJHKsource, gpsPointSource, reliableGcsPointSource, reliableGpsPointSource WSA Offset of 2nd epoch K detection from master position (+east/-west) real 4 arcsec -0.9999995e9 POS_EQ_RA_OFF

k_2Xi gcsSource, gpsSource WSA Offset of 2nd epoch K 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.

k_3AperMag3 gpsJHKsource, gpsPointSource, reliableGpsPointSource WSA Default point/extended source 3rd epoch K aperture corrected mag (2.0 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_3AperMag3 gpsSource WSA Default point/extended source 3rd epoch K aperture corrected mag (2.0 arcsec aperture diameter)
If in doubt use this flux estimator real 4 mag -0.9999995e9 PHOT_MAG

k_3AperMag3Err gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Error in default point/extended source 3rd epoch K mag (2.0 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_3AperMag4 gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Extended source 3rd epoch K aperture corrected mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_3AperMag4Err gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Error in extended source 3rd epoch K mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_3AperMag6 gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Extended source 3rd epoch K aperture corrected mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

k_3AperMag6Err gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Error in extended source 3rd epoch K mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

k_3Class gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGpsPointSource WSA discrete image classification flag in 3rd epoch K smallint 2 -9999 CLASS_MISC

k_3ClassStat gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGpsPointSource WSA N(0,1) stellarness-of-profile statistic in 3rd epoch K real 4 -0.9999995e9 STAT_PROP

k_3Deblend gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGpsPointSource WSA flag indicating parent/child relation in 3rd epoch K int 4 -99999999 CODE_MISC

k_3Ell gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGpsPointSource WSA 1-b/a, where a/b=semi-major/minor axes in 3rd epoch K real 4 -0.9999995e9 PHYS_ELLIPTICITY

k_3eNum gpsJHKmergeLog, gpsMergeLog WSA the extension number of this 3rd epoch K frame tinyint 1 NUMBER

k_3ErrBits gpsJHKsource, gpsPointSource, gpsSourceRemeasurement, reliableGpsPointSource WSA processing warning/error bitwise flags in 3rd epoch K int 4 -99999999 CODE_MISC

k_3ErrBits gpsSource WSA processing warning/error bitwise flags in 3rd epoch K 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.

k_3Eta gpsJHKsource, gpsPointSource, reliableGpsPointSource WSA Offset of 3rd epoch K detection from master position (+north/-south) real 4 arcsec -0.9999995e9 POS_EQ_DEC_OFF

k_3Eta gpsSource WSA Offset of 3rd epoch K 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.

k_3Gausig gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGpsPointSource WSA RMS of axes of ellipse fit in 3rd epoch K real 4 pixels -0.9999995e9 MORPH_PARAM

k_3HallMag gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Total point source 3rd epoch K mag real 4 mag -0.9999995e9 PHOT_MAG

k_3HallMagErr gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Error in total point source 3rd epoch K mag real 4 mag -0.9999995e9 ERROR

k_3Mag gpsSourceRemeasurement WSA 3rd epoch K mag (as appropriate for this merged source) real 4 mag -0.9999995e9 PHOT_MAG

k_3MagErr gpsSourceRemeasurement WSA Error in 3rd epoch K mag real 4 mag -0.9999995e9 ERROR

k_3mfID gpsJHKmergeLog, gpsMergeLog WSA the UID of the relevant 3rd epoch K multiframe bigint 8 ID_FRAME

k_3ObjID gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA the UID of the 3rd epoch K detection bigint 8 -99999999 ID_NUMBER

k_3ObjID gpsSourceRemeasurement WSA the UID of the 3rd epoch K remeasurement bigint 8 -99999999 ID_NUMBER

k_3PA gpsJHKsource, gpsPointSource, gpsSource, gpsSourceRemeasurement, reliableGpsPointSource WSA ellipse fit celestial orientation in 3rd epoch K real 4 Degrees -0.9999995e9 POS_POS-ANG

k_3PetroMag gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Extended source 3rd epoch K mag (Petrosian) real 4 mag -0.9999995e9 PHOT_MAG

k_3PetroMagErr gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Error in extended source 3rd epoch K mag (Petrosian) real 4 mag -0.9999995e9 ERROR

k_3ppErrBits gpsJHKsource, gpsPointSource, gpsSourceRemeasurement, reliableGpsPointSource WSA additional WFAU post-processing error bits in 3rd epoch K int 4 0 CODE_MISC

k_3ppErrBits gpsSource WSA additional WFAU post-processing error bits in 3rd epoch K 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.

k_3PsfMag gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Point source profile-fitted 3rd epoch K mag real 4 mag -0.9999995e9 PHOT_MAG

k_3PsfMagErr gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Error in point source profile-fitted 3rd epoch K mag real 4 mag -0.9999995e9 ERROR

k_3SeqNum gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA the running number of the 3rd epoch K detection int 4 -99999999 ID_NUMBER

k_3SeqNum gpsSourceRemeasurement WSA the running number of the 3rd epoch K remeasurement int 4 -99999999 ID_NUMBER

k_3SerMag2D gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Extended source 3rd epoch K mag (profile-fitted) real 4 mag -0.9999995e9 PHOT_MAG

k_3SerMag2DErr gpsJHKsource, gpsPointSource, gpsSource, reliableGpsPointSource WSA Error in extended source 3rd epoch K mag (profile-fitted) real 4 mag -0.9999995e9 ERROR

k_3Xi gpsJHKsource, gpsPointSource, reliableGpsPointSource WSA Offset of 3rd epoch K detection from master position (+east/-west) real 4 arcsec -0.9999995e9 POS_EQ_RA_OFF

k_3Xi gpsSource WSA Offset of 3rd epoch K 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.

k_5sig_ba twomass_xsc 2MASS K minor/major axis ratio fit to the 5-sigma isophote. real 4 PHYS_AXIS-RATIO

k_5sig_phi twomass_xsc 2MASS K angle to 5-sigma major axis (E of N). smallint 2 degrees ERROR

k_5surf twomass_xsc 2MASS K central surface brightness (r<=5). real 4 mag PHOT_SB_GENERAL

k_ba twomass_xsc 2MASS K minor/major axis ratio fit to the 3-sigma isophote. real 4 PHYS_AXIS-RATIO

k_back twomass_xsc 2MASS K coadd median background. real 4 CODE_MISC

k_bisym_chi twomass_xsc 2MASS K bi-symmetric cross-correlation chi. real 4 FIT_PARAM_VALUE

k_bisym_rat twomass_xsc 2MASS K bi-symmetric flux ratio. real 4 PHOT_FLUX_RATIO

k_bndg_amp twomass_xsc 2MASS K banding maximum FT amplitude on this side of coadd. real 4 DN FIT_PARAM_VALUE

k_bndg_per twomass_xsc 2MASS K banding Fourier Transf. period on this side of coadd. int 4 arcsec FIT_PARAM_VALUE

k_chif_ellf twomass_xsc 2MASS K % chi-fraction for elliptical fit to 3-sig isophote. real 4 FIT_PARAM_VALUE

k_cmsig twomass_psc 2MASS Corrected photometric uncertainty for the default Ks-band magnitude. real 4 mag SPECT_FLUX_VALUE

k_con_indx twomass_xsc 2MASS K concentration index r_75%/r_25%. real 4 PHYS_CONCENT_INDEX

k_d_area twomass_xsc 2MASS K 5-sigma to 3-sigma differential area. smallint 2 FIT_RESIDUAL

k_flg_10 twomass_xsc 2MASS K confusion flag for 10 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_15 twomass_xsc 2MASS K confusion flag for 15 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_20 twomass_xsc 2MASS K confusion flag for 20 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_25 twomass_xsc 2MASS K confusion flag for 25 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_30 twomass_xsc 2MASS K confusion flag for 30 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_40 twomass_xsc 2MASS K confusion flag for 40 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_5 twomass_xsc 2MASS K confusion flag for 5 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_50 twomass_xsc 2MASS K confusion flag for 50 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_60 twomass_xsc 2MASS K confusion flag for 60 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_7 twomass_xsc 2MASS K confusion flag for 7 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_70 twomass_xsc 2MASS K confusion flag for 70 arcsec circular ap. mag. smallint 2 CODE_MISC

k_flg_c twomass_xsc 2MASS K confusion flag for Kron circular mag. smallint 2 CODE_MISC

k_flg_e twomass_xsc 2MASS K confusion flag for Kron elliptical mag. smallint 2 CODE_MISC

k_flg_fc twomass_xsc 2MASS K confusion flag for fiducial Kron circ. mag. smallint 2 CODE_MISC

k_flg_fe twomass_xsc 2MASS K confusion flag for fiducial Kron ell. mag. smallint 2 CODE_MISC

k_flg_i20c twomass_xsc 2MASS K confusion flag for 20mag/sq." iso. circ. mag. smallint 2 CODE_MISC

k_flg_i20e twomass_xsc 2MASS K confusion flag for 20mag/sq." iso. ell. mag. smallint 2 CODE_MISC

k_flg_i21c twomass_xsc 2MASS K confusion flag for 21mag/sq." iso. circ. mag. smallint 2 CODE_MISC

k_flg_i21e twomass_xsc 2MASS K confusion flag for 21mag/sq." iso. ell. mag. smallint 2 CODE_MISC

k_flg_j21fc twomass_xsc 2MASS K confusion flag for 21mag/sq." iso. fid. circ. mag. smallint 2 CODE_MISC

k_flg_j21fe twomass_xsc 2MASS K confusion flag for 21mag/sq." iso. fid. ell. mag. smallint 2 CODE_MISC

k_flg_k20fc twomass_xsc 2MASS K confusion flag for 20mag/sq." iso. fid. circ. mag. smallint 2 CODE_MISC

k_flg_k20fe twomass_xsc 2MASS K confusion flag for 20mag/sq." iso. fid. ell. mag. smallint 2 CODE_MISC

k_m twomass_psc 2MASS Default Ks-band magnitude real 4 mag SPECT_FLUX_VALUE

k_m_10 twomass_xsc 2MASS K 10 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_15 twomass_xsc 2MASS K 15 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_20 twomass_xsc 2MASS K 20 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_25 twomass_xsc 2MASS K 25 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_30 twomass_xsc 2MASS K 30 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_40 twomass_xsc 2MASS K 40 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_5 twomass_xsc 2MASS K 5 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_50 twomass_xsc 2MASS K 50 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_60 twomass_xsc 2MASS K 60 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_7 twomass_xsc 2MASS K 7 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_70 twomass_xsc 2MASS K 70 arcsec radius circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_c twomass_xsc 2MASS K Kron circular aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_e twomass_xsc 2MASS K Kron elliptical aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_ext twomass_xsc 2MASS K mag from fit extrapolation. real 4 mag SPECT_FLUX_VALUE

k_m_fc twomass_xsc 2MASS K fiducial Kron circular magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_fe twomass_xsc 2MASS K fiducial Kron ell. mag aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_i20c twomass_xsc 2MASS K 20mag/sq." isophotal circular ap. magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_i20e twomass_xsc 2MASS K 20mag/sq." isophotal elliptical ap. magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_i21c twomass_xsc 2MASS K 21mag/sq." isophotal circular ap. magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_i21e twomass_xsc 2MASS K 21mag/sq." isophotal elliptical ap. magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_j21fc twomass_xsc 2MASS K 21mag/sq." isophotal fiducial circ. ap. mag. real 4 mag SPECT_FLUX_VALUE

k_m_j21fe twomass_xsc 2MASS K 21mag/sq." isophotal fiducial ell. ap. magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_k20fc twomass_xsc 2MASS K 20mag/sq." isophotal fiducial circ. ap. mag. real 4 mag SPECT_FLUX_VALUE

k_m_k20fe twomass_xsc 2MASS K 20mag/sq." isophotal fiducial ell. ap. magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_stdap twomass_psc 2MASS Ks-band "standard" aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_m_sys twomass_xsc 2MASS K system photometry magnitude. real 4 mag SPECT_FLUX_VALUE

k_mnsurfb_eff twomass_xsc 2MASS K mean surface brightness at the half-light radius. real 4 mag PHOT_SB_GENERAL

k_msig_10 twomass_xsc 2MASS K 1-sigma uncertainty in 10 arcsec circular ap. mag. real 4 mag ERROR

k_msig_15 twomass_xsc 2MASS K 1-sigma uncertainty in 15 arcsec circular ap. mag. real 4 mag ERROR

k_msig_20 twomass_xsc 2MASS K 1-sigma uncertainty in 20 arcsec circular ap. mag. real 4 mag ERROR

k_msig_25 twomass_xsc 2MASS K 1-sigma uncertainty in 25 arcsec circular ap. mag. real 4 mag ERROR

k_msig_30 twomass_xsc 2MASS K 1-sigma uncertainty in 30 arcsec circular ap. mag. real 4 mag ERROR

k_msig_40 twomass_xsc 2MASS K 1-sigma uncertainty in 40 arcsec circular ap. mag. real 4 mag ERROR

k_msig_5 twomass_xsc 2MASS K 1-sigma uncertainty in 5 arcsec circular ap. mag. real 4 mag ERROR

k_msig_50 twomass_xsc 2MASS K 1-sigma uncertainty in 50 arcsec circular ap. mag. real 4 mag ERROR

k_msig_60 twomass_xsc 2MASS K 1-sigma uncertainty in 60 arcsec circular ap. mag. real 4 mag ERROR

k_msig_7 twomass_xsc 2MASS K 1-sigma uncertainty in 7 arcsec circular ap. mag. real 4 mag ERROR

k_msig_70 twomass_xsc 2MASS K 1-sigma uncertainty in 70 arcsec circular ap. mag. real 4 mag ERROR

k_msig_c twomass_xsc 2MASS K 1-sigma uncertainty in Kron circular mag. real 4 mag ERROR

k_msig_e twomass_xsc 2MASS K 1-sigma uncertainty in Kron elliptical mag. real 4 mag ERROR

k_msig_ext twomass_xsc 2MASS K 1-sigma uncertainty in mag from fit extrapolation. real 4 mag ERROR

k_msig_fc twomass_xsc 2MASS K 1-sigma uncertainty in fiducial Kron circ. mag. real 4 mag ERROR

k_msig_fe twomass_xsc 2MASS K 1-sigma uncertainty in fiducial Kron ell. mag. real 4 mag ERROR

k_msig_i20c twomass_xsc 2MASS K 1-sigma uncertainty in 20mag/sq." iso. circ. mag. real 4 mag ERROR

k_msig_i20e twomass_xsc 2MASS K 1-sigma uncertainty in 20mag/sq." iso. ell. mag. real 4 mag ERROR

k_msig_i21c twomass_xsc 2MASS K 1-sigma uncertainty in 21mag/sq." iso. circ. mag. real 4 mag ERROR

k_msig_i21e twomass_xsc 2MASS K 1-sigma uncertainty in 21mag/sq." iso. ell. mag. real 4 mag ERROR

k_msig_j21fc twomass_xsc 2MASS K 1-sigma uncertainty in 21mag/sq." iso.fid.circ.mag. real 4 mag ERROR

k_msig_j21fe twomass_xsc 2MASS K 1-sigma uncertainty in 21mag/sq." iso.fid.ell.mag. real 4 mag ERROR

k_msig_k20fc twomass_xsc 2MASS K 1-sigma uncertainty in 20mag/sq." iso.fid.circ. mag. real 4 mag ERROR

k_msig_k20fe twomass_xsc 2MASS K 1-sigma uncertainty in 20mag/sq." iso.fid.ell.mag. real 4 mag ERROR

k_msig_stdap twomass_psc 2MASS Uncertainty in the Ks-band standard aperture magnitude. real 4 mag SPECT_FLUX_VALUE

k_msig_sys twomass_xsc 2MASS K 1-sigma uncertainty in system photometry mag. real 4 mag ERROR

k_msigcom twomass_psc 2MASS Combined, or total photometric uncertainty for the default Ks-band magnitude. real 4 mag SPECT_FLUX_VALUE

k_msnr10 twomass_scn 2MASS The estimated Ks-band magnitude at which SNR=10 is achieved for this scan. real 4 mag SPECT_FLUX_VALUE

k_n_snr10 twomass_scn 2MASS Number of point sources at Ks-band with SNR>10 (instrumental mag <=14.3) int 4 NUMBER

k_pchi twomass_xsc 2MASS K chi^2 of fit to rad. profile (LCSB: alpha scale len). real 4 FIT_PARAM_VALUE

k_peak twomass_xsc 2MASS K peak pixel brightness. real 4 mag PHOT_SB_GENERAL

k_perc_darea twomass_xsc 2MASS K 5-sigma to 3-sigma percent area change. smallint 2 FIT_PARAM

k_phi twomass_xsc 2MASS K angle to 3-sigma major axis (E of N). smallint 2 degrees POS_POS-ANG

k_psfchi twomass_psc 2MASS Reduced chi-squared goodness-of-fit value for the Ks-band profile-fit photometry made on the 1.3 s "Read_2" exposures. real 4 FIT_PARAM_VALUE

k_psp twomass_scn 2MASS Ks-band photometric sensitivity paramater (PSP). real 4 INST_SENSITIVITY

k_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 Ks-band photometric errors and is expressed in units of mJy. real 4 INST_NOISE

k_r_c twomass_xsc 2MASS K Kron circular aperture radius. real 4 arcsec EXTENSION_RAD

k_r_e twomass_xsc 2MASS K Kron elliptical aperture semi-major axis. real 4 arcsec EXTENSION_RAD

k_r_eff twomass_xsc 2MASS K half-light (integrated half-flux point) radius. real 4 arcsec EXTENSION_RAD

k_r_i20c twomass_xsc 2MASS K 20mag/sq." isophotal circular aperture radius. real 4 arcsec EXTENSION_RAD

k_r_i20e twomass_xsc 2MASS K 20mag/sq." isophotal elliptical ap. semi-major axis. real 4 arcsec EXTENSION_RAD

k_r_i21c twomass_xsc 2MASS K 21mag/sq." isophotal circular aperture radius. real 4 arcsec EXTENSION_RAD

k_r_i21e twomass_xsc 2MASS K 21mag/sq." isophotal elliptical ap. semi-major axis. real 4 arcsec EXTENSION_RAD

k_resid_ann twomass_xsc 2MASS K residual annulus background median. real 4 DN CODE_MISC

k_sc_1mm twomass_xsc 2MASS K 1st moment (score) (LCSB: super blk 2,4,8 SNR). real 4 CODE_MISC

k_sc_2mm twomass_xsc 2MASS K 2nd moment (score) (LCSB: SNRMAX - super SNR max). real 4 CODE_MISC

k_sc_msh twomass_xsc 2MASS K median shape score. real 4 CODE_MISC

k_sc_mxdn twomass_xsc 2MASS K mxdn (score) (LCSB: BSNR - block/smoothed SNR). real 4 CODE_MISC

k_sc_r1 twomass_xsc 2MASS K r1 (score). real 4 CODE_MISC

k_sc_r23 twomass_xsc 2MASS K r23 (score) (LCSB: TSNR - integrated SNR for r=15). real 4 CODE_MISC

k_sc_sh twomass_xsc 2MASS K shape (score). real 4 CODE_MISC

k_sc_vint twomass_xsc 2MASS K vint (score). real 4 CODE_MISC

k_sc_wsh twomass_xsc 2MASS K wsh (score) (LCSB: PSNR - peak raw SNR). real 4 CODE_MISC

k_seetrack twomass_xsc 2MASS K band seetracking score. real 4 CODE_MISC

k_sh0 twomass_xsc 2MASS K ridge shape (LCSB: BSNR limit). real 4 FIT_PARAM

k_shape_avg twomass_scn 2MASS Ks-band average seeing shape for scan. real 4 INST_SEEING

k_shape_rms twomass_scn 2MASS RMS-error of Ks-band average seeing shape. real 4 INST_SEEING

k_sig_sh0 twomass_xsc 2MASS K ridge shape sigma (LCSB: B2SNR limit). real 4 FIT_PARAM

k_snr twomass_psc 2MASS Ks-band "scan" signal-to-noise ratio. real 4 mag INST_NOISE

k_subst2 twomass_xsc 2MASS K residual background #2 (score). real 4 CODE_MISC

k_zp_ap twomass_scn 2MASS Photometric zero-point for Ks-band aperture photometry. real 4 mag PHOT_ZP

k_zperr_ap twomass_scn 2MASS RMS-error of zero-point for Ks-band aperture photometry real 4 mag FIT_ERROR

kAperMag3 dxsJKsource, lasExtendedSource, lasPointSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Default point/extended source K aperture corrected mag (2.0 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

kAperMag3 dxsSource, lasSource WSA Default point/extended source K aperture corrected mag (2.0 arcsec aperture diameter)
If in doubt use this flux estimator real 4 mag -0.9999995e9 PHOT_MAG

kAperMag3 udsSource WSA Default point/extended source K mag, no aperture correction applied
If in doubt use this flux estimator real 4 mag -0.9999995e9 PHOT_MAG

kAperMag3Err dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource WSA Error in default point/extended source K mag (2.0 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

kAperMag4 dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Extended source K aperture corrected mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

kAperMag4 udsSource WSA Extended source K mag, no aperture correction applied real 4 mag -0.9999995e9 PHOT_MAG

kAperMag4Err dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource WSA Error in extended source K mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

kAperMag6 dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Extended source K aperture corrected mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG

kAperMag6 udsSource WSA Extended source K mag, no aperture correction applied real 4 mag -0.9999995e9 PHOT_MAG

kAperMag6Err dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource WSA Error in extended source K mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR

kClass dxsJKsource, dxsSource, dxsSourceRemeasurement, lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource, udsSourceRemeasurement WSA discrete image classification flag in K smallint 2 -9999 CLASS_MISC

kClassStat dxsJKsource, dxsSource, dxsSourceRemeasurement, lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSourceRemeasurement WSA N(0,1) stellarness-of-profile statistic in K real 4 -0.9999995e9 STAT_PROP

kClassStat udsSource WSA S-Extractor classification statistic in K real 4 -0.9999995e9 STAT_PROP

kDeblend dxsJKsource, dxsSource, dxsSourceRemeasurement, lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource, udsSourceRemeasurement WSA flag indicating parent/child relation in K int 4 -99999999 CODE_MISC

kEll dxsJKsource, dxsSource, dxsSourceRemeasurement, lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource, udsSourceRemeasurement WSA 1-b/a, where a/b=semi-major/minor axes in K real 4 -0.9999995e9 PHYS_ELLIPTICITY

keNum dxsJKmergeLog, dxsMergeLog, lasMergeLog, lasYJHKmergeLog, udsMergeLog WSA the extension number of this K frame tinyint 1 NUMBER

kErrBits dxsJKsource, dxsSourceRemeasurement, lasExtendedSource, lasPointSource, lasSourceRemeasurement, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSourceRemeasurement WSA processing warning/error bitwise flags in K int 4 -99999999 CODE_MISC

kErrBits dxsSource, lasSource WSA processing warning/error bitwise flags in K 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.

kErrBits udsSource WSA processing warning/error bitwise flags in K 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

kEta dxsJKsource, lasExtendedSource, lasPointSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Offset of K detection from master position (+north/-south) real 4 arcsec -0.9999995e9 POS_EQ_DEC_OFF

kEta dxsSource, lasSource, udsSource WSA Offset of K 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.

kGausig dxsJKsource, dxsSource, dxsSourceRemeasurement, lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource, udsSourceRemeasurement WSA RMS of axes of ellipse fit in K real 4 pixels -0.9999995e9 MORPH_PARAM

kHallMag dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Total point source K mag real 4 mag -0.9999995e9 PHOT_MAG

kHallMag udsSource WSA Not available in SE output real 4 mag -0.9999995e9 PHOT_MAG

kHallMagErr dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Error in total point source K mag real 4 mag -0.9999995e9 ERROR

kHallMagErr udsSource WSA Not available in SE output real 4 mag -0.9999995e9 ERROR

kMag CurrentStdStarInfo, PreviousStdStarInfo WSA K band total magnitude of star (from external sources if primary) real 4 mag PHOT_INT-MAG

kMag dxsSourceRemeasurement, lasSourceRemeasurement, udsSourceRemeasurement WSA K mag (as appropriate for this merged source) real 4 mag -0.9999995e9 PHOT_MAG

kMag ukirtFSstars WSA K band total magnitude on the MKO(UFTI) system real 4 mag PHOT_INT-MAG

kMagErr CurrentStdStarInfo, PreviousStdStarInfo WSA K band magnitude error of star real 4 mag ERROR

kMagErr dxsSourceRemeasurement, lasSourceRemeasurement, udsSourceRemeasurement WSA Error in K mag real 4 mag -0.9999995e9 ERROR

kMagErr ukirtFSstars WSA K band magnitude error real 4 mag ERROR

kmfID dxsJKmergeLog, dxsMergeLog, lasMergeLog, lasYJHKmergeLog, udsMergeLog WSA the UID of the relevant K multiframe bigint 8 ID_FRAME

kObjID dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource WSA the UID of the K detection bigint 8 -99999999 ID_NUMBER

kObjID dxsSourceRemeasurement, lasSourceRemeasurement, udsSourceRemeasurement WSA the UID of the K remeasurement bigint 8 -99999999 ID_NUMBER

kPA dxsJKsource, dxsSource, dxsSourceRemeasurement, lasExtendedSource, lasPointSource, lasSource, lasSourceRemeasurement, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource, udsSourceRemeasurement WSA ellipse fit celestial orientation in K real 4 Degrees -0.9999995e9 POS_POS-ANG

kPetroMag dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource WSA Extended source K mag (Petrosian) real 4 mag -0.9999995e9 PHOT_MAG

kPetroMagErr dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource WSA Error in extended source K mag (Petrosian) real 4 mag -0.9999995e9 ERROR

kppErrBits dxsJKsource, dxsSourceRemeasurement, lasExtendedSource, lasPointSource, lasSourceRemeasurement, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource, udsSourceRemeasurement WSA additional WFAU post-processing error bits in K int 4 0 CODE_MISC

kppErrBits dxsSource, lasSource WSA additional WFAU post-processing error bits in K 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.

kPsfMag dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Point source profile-fitted K mag real 4 mag -0.9999995e9 PHOT_MAG

kPsfMag udsSource WSA Not available in SE output real 4 mag -0.9999995e9 PHOT_MAG

kPsfMagErr dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Error in point source profile-fitted K mag real 4 mag -0.9999995e9 ERROR

kPsfMagErr udsSource WSA Not available in SE output real 4 mag -0.9999995e9 ERROR

kronFlux UKIDSSDetection WSA flux within circular aperture to k × r_k ; k = 2 real 4 ADU PHOT_INTENSITY_ADU

kronFlux dxsDetection, dxsListRemeasurement, gcsDetection, gcsListRemeasurement, gpsDetection, gpsListRemeasurement, lasDetection, lasListRemeasurement, udsListRemeasurement WSA flux within circular aperture to k × r_k ; k = 2 {catalogue TType keyword: Kron_flux} real 4 ADU PHOT_INTENSITY_ADU

kronFlux ptsDetection WSATransit flux within circular aperture to k × r_k ; k = 2 {catalogue TType keyword: Kron_flux} real 4 ADU PHOT_INTENSITY_ADU

kronFlux udsDetection WSA flux within Kron radius circular aperture (SE: FLUX_AUTO) {catalogue TType keyword: Kron_flux} real 4 ADU PHOT_INTENSITY_ADU

kronFluxErr UKIDSSDetection WSA error on Kron flux real 4 ADU ERROR

kronFluxErr dxsDetection, dxsListRemeasurement, gcsDetection, gcsListRemeasurement, gpsDetection, gpsListRemeasurement, lasDetection, lasListRemeasurement, udsListRemeasurement WSA error on Kron flux {catalogue TType keyword: Kron_flux_err} real 4 ADU ERROR

kronFluxErr ptsDetection WSATransit error on Kron flux {catalogue TType keyword: Kron_flux_err} real 4 ADU ERROR

kronFluxErr udsDetection WSA error on Kron flux (SE: FLUXERR_AUTO) {catalogue TType keyword: Kron_flux_err} real 4 ADU ERROR

kronMag dxsDetection, dxsListRemeasurement, gcsDetection, gcsListRemeasurement, gpsDetection, gpsListRemeasurement, lasDetection, lasListRemeasurement, UKIDSSDetection, udsDetection, udsListRemeasurement WSA Calibrated Kron magnitude within circular aperture r_k real 4 mag PHOT_INT-MAG

kronMag ptsDetection WSATransit Calibrated Kron magnitude within circular aperture r_k real 4 mag PHOT_INT-MAG

kronMagErr dxsDetection, dxsListRemeasurement, gcsDetection, gcsListRemeasurement, gpsDetection, gpsListRemeasurement, lasDetection, lasListRemeasurement, UKIDSSDetection, udsDetection, udsListRemeasurement WSA error on calibrated Kron magnitude real 4 mag ERROR

kronMagErr ptsDetection WSATransit error on calibrated Kron magnitude real 4 mag ERROR

kronRad UKIDSSDetection WSA r_k as defined in Bertin and Arnouts 1996 A&A Supp 117 393 real 4 pixels EXTENSION_RAD

kronRad dxsDetection, dxsListRemeasurement, gcsDetection, gcsListRemeasurement, gpsDetection, gpsListRemeasurement, lasDetection, lasListRemeasurement, udsListRemeasurement WSA r_k as defined in Bertin and Arnouts 1996 A&A Supp 117 393 {catalogue TType keyword: Kron_radius} real 4 pixels EXTENSION_RAD

kronRad ptsDetection WSATransit r_k as defined in Bertin and Arnouts 1996 A&A Supp 117 393 {catalogue TType keyword: Kron_radius} real 4 pixels EXTENSION_RAD

kronRad udsDetection WSA Kron radius as defined in SE by Graham and Driver (2005) (SE: KRON_RADIUS*A_IMAGE) {catalogue TType keyword: Kron_radius}
r_k = ∑R² I(R) / ∑R I(R) real 4 pixels EXTENSION_RAD

Since <FLUX>_RADIUS is expressed in multiples of the major axis, <FLUX>_RADIUS is multiplied by A_IMAGE to convert to pixels.

kSeqNum dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource, udsSource WSA the running number of the K detection int 4 -99999999 ID_NUMBER

kSeqNum dxsSourceRemeasurement, lasSourceRemeasurement, udsSourceRemeasurement WSA the running number of the K remeasurement int 4 -99999999 ID_NUMBER

kSerMag2D dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Extended source K mag (profile-fitted) real 4 mag -0.9999995e9 PHOT_MAG

kSerMag2D udsSource WSA Not available in SE output real 4 mag -0.9999995e9 PHOT_MAG

kSerMag2DErr dxsJKsource, dxsSource, lasExtendedSource, lasPointSource, lasSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Error in extended source K mag (profile-fitted) real 4 mag -0.9999995e9 ERROR

kSerMag2DErr udsSource WSA Not available in SE output real 4 mag -0.9999995e9 ERROR

kXi dxsJKsource, lasExtendedSource, lasPointSource, lasYJHKsource, reliableDxsSource, reliableLasPointSource WSA Offset of K detection from master position (+east/-west) real 4 arcsec -0.9999995e9 POS_EQ_RA_OFF

kXi dxsSource, lasSource, udsSource WSA Offset of K 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.

WFAU, Institute for Astronomy,
Royal Observatory, Blackford Hill
Edinburgh, EH9 3HJ, UK
Tel +44 131 668 8356 (office)
or +44 131 668 8100 (switchboard)

wsa-support@roe.ac.uk
27/01/2009