Y 
Name  Schema Table  Database  Description  Type  Length  Unit  Default Value  Unified Content Descriptor 
y 
[nspid]Detection 
WSA NonSurvey 
Y coordinate of detection {catalogue TType keyword: Y_coordinate} Intensityweighted isophotal centreofgravity in Y. 
real 
4 
pixels 

POS_PLATE_Y 
y_1AperMag3 
[nspid]Source 
WSA NonSurvey 
Default point source Y_1 aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_1AperMag3Err 
[nspid]Source 
WSA NonSurvey 
Error in default point source Y_1 mag (2.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_1AperMag4 
[nspid]Source 
WSA NonSurvey 
Point source Y_1 aperture corrected mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_1AperMag4Err 
[nspid]Source 
WSA NonSurvey 
Error in point source Y_1 mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_1AperMag6 
[nspid]Source 
WSA NonSurvey 
Point source Y_1 aperture corrected mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_1AperMag6Err 
[nspid]Source 
WSA NonSurvey 
Error in point source Y_1 mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_1Class 
[nspid]Source 
WSA NonSurvey 
discrete image classification flag in Y_1 
smallint 
2 

9999 
CLASS_MISC 
y_1ClassStat 
[nspid]Source 
WSA NonSurvey 
N(0,1) stellarnessofprofile statistic in Y_1 
real 
4 

0.9999995e9 
STAT_PROP 
y_1Deblend 
[nspid]Source 
WSA NonSurvey 
placeholder flag indicating parent/child relation in Y_1 
int 
4 

99999999 
CODE_MISC 
This CASU pipeline processing source extraction flag is a placeholder only, and is always set to zero in all passbands in the merged source lists. If you need to know when a particular image detection is a component of a deblend or not, test bit 4 of attribute ppErrBits (see corresponding glossary entry) which is set by WFAU's postprocessing software based on testing the areal profiles aprof28 (these are set by CASU to 1 for deblended components, or positive values for nondeblended detections). We encode this in an information bit of ppErrBits for convenience when querying the merged source tables. 
y_1Ell 
[nspid]Source 
WSA NonSurvey 
1b/a, where a/b=semimajor/minor axes in Y_1 
real 
4 

0.9999995e9 
PHYS_ELLIPTICITY 
y_1eNum 
[nspid]MergeLog 
WSA NonSurvey 
the extension number of this Y_1 frame 
tinyint 
1 


NUMBER 
y_1ErrBits 
[nspid]Source 
WSA NonSurvey 
processing warning/error bitwise flags in Y_1 
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. 
y_1Eta 
[nspid]Source 
WSA NonSurvey 
Offset of Y_1 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; UHS; also nonsurvey 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. NB: the master position is the position of the detection in the shortest passband in the set, rather than the ra/dec of the source as stored in source attributes of the same name. The former is used in the pairing process, while the latter is generally the optimally weighted mean position from an astrometric solution or other combinatorial process of all individual detection positions across the available passbands. 
y_1Gausig 
[nspid]Source 
WSA NonSurvey 
RMS of axes of ellipse fit in Y_1 
real 
4 
pixels 
0.9999995e9 
MORPH_PARAM 
y_1HallMag 
[nspid]Source 
WSA NonSurvey 
Total point source Y_1 mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_1HallMagErr 
[nspid]Source 
WSA NonSurvey 
Error in total point source Y_1 mag 
real 
4 
mag 
0.9999995e9 
ERROR 
y_1mfID 
[nspid]MergeLog 
WSA NonSurvey 
the UID of the relevant Y_1 multiframe 
bigint 
8 


ID_FRAME 
y_1mj_1Ext 
[nspid]Source 
WSA NonSurvey 
Extended source colour Y_1J_1 (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
y_1mj_1ExtErr 
[nspid]Source 
WSA NonSurvey 
Error on extended source colour Y_1J_1 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
y_1mj_1Pnt 
[nspid]Source 
WSA NonSurvey 
Point source colour Y_1J_1 (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
y_1mj_1PntErr 
[nspid]Source 
WSA NonSurvey 
Error on point source colour Y_1J_1 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
y_1PA 
[nspid]Source 
WSA NonSurvey 
ellipse fit celestial orientation in Y_1 
real 
4 
Degrees 
0.9999995e9 
POS_POSANG 
y_1PetroMag 
[nspid]Source 
WSA NonSurvey 
Extended source Y_1 mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_1PetroMagErr 
[nspid]Source 
WSA NonSurvey 
Error in extended source Y_1 mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_1ppErrBits 
[nspid]Source 
WSA NonSurvey 
additional WFAU postprocessing error bits in Y_1 
int 
4 

0 
CODE_MISC 
Postprocessing 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 4byte 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  All VDFS catalogues  0  6  Bad pixel(s) in default aperture  64  0x00000040  All VDFS catalogues  1  15  Source in poor flat field region  32768  0x00008000  All but mosaics  2  16  Close to saturated  65536  0x00010000  All VDFS catalogues (though deeps excluded prior to DR8)  2  17  Photometric calibration probably subject to systematic error  131072  0x00020000  GPS only  2  19  Possible crosstalk artefact/contamination  524288  0x00080000  All but GPS  2  22  Lies within a dither offset of the stacked frame boundary  4194304  0x00400000  All but mosaics  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. 
y_1PsfMag 
[nspid]Source 
WSA NonSurvey 
Point source profilefitted Y_1 mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_1PsfMagErr 
[nspid]Source 
WSA NonSurvey 
Error in point source profilefitted Y_1 mag 
real 
4 
mag 
0.9999995e9 
ERROR 
y_1SeqNum 
[nspid]Source 
WSA NonSurvey 
the running number of the Y_1 detection 
int 
4 

99999999 
ID_NUMBER 
y_1SerMag2D 
[nspid]Source 
WSA NonSurvey 
Extended source Y_1 mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_1SerMag2DErr 
[nspid]Source 
WSA NonSurvey 
Error in extended source Y_1 mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_1Xi 
[nspid]Source 
WSA NonSurvey 
Offset of Y_1 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; UHS; also nonsurvey 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. NB: the master position is the position of the detection in the shortest passband in the set, rather than the ra/dec of the source as stored in source attributes of the same name. The former is used in the pairing process, while the latter is generally the optimally weighted mean position from an astrometric solution or other combinatorial process of all individual detection positions across the available passbands. 
y_2AperMag3 
[nspid]Source 
WSA NonSurvey 
Default point source Y_2 aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_2AperMag3Err 
[nspid]Source 
WSA NonSurvey 
Error in default point source Y_2 mag (2.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_2AperMag4 
[nspid]Source 
WSA NonSurvey 
Point source Y_2 aperture corrected mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_2AperMag4Err 
[nspid]Source 
WSA NonSurvey 
Error in point source Y_2 mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_2AperMag6 
[nspid]Source 
WSA NonSurvey 
Point source Y_2 aperture corrected mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_2AperMag6Err 
[nspid]Source 
WSA NonSurvey 
Error in point source Y_2 mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_2Class 
[nspid]Source 
WSA NonSurvey 
discrete image classification flag in Y_2 
smallint 
2 

9999 
CLASS_MISC 
y_2ClassStat 
[nspid]Source 
WSA NonSurvey 
N(0,1) stellarnessofprofile statistic in Y_2 
real 
4 

0.9999995e9 
STAT_PROP 
y_2Deblend 
[nspid]Source 
WSA NonSurvey 
placeholder flag indicating parent/child relation in Y_2 
int 
4 

99999999 
CODE_MISC 
This CASU pipeline processing source extraction flag is a placeholder only, and is always set to zero in all passbands in the merged source lists. If you need to know when a particular image detection is a component of a deblend or not, test bit 4 of attribute ppErrBits (see corresponding glossary entry) which is set by WFAU's postprocessing software based on testing the areal profiles aprof28 (these are set by CASU to 1 for deblended components, or positive values for nondeblended detections). We encode this in an information bit of ppErrBits for convenience when querying the merged source tables. 
y_2Ell 
[nspid]Source 
WSA NonSurvey 
1b/a, where a/b=semimajor/minor axes in Y_2 
real 
4 

0.9999995e9 
PHYS_ELLIPTICITY 
y_2eNum 
[nspid]MergeLog 
WSA NonSurvey 
the extension number of this Y_2 frame 
tinyint 
1 


NUMBER 
y_2ErrBits 
[nspid]Source 
WSA NonSurvey 
processing warning/error bitwise flags in Y_2 
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. 
y_2Eta 
[nspid]Source 
WSA NonSurvey 
Offset of Y_2 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; UHS; also nonsurvey 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. NB: the master position is the position of the detection in the shortest passband in the set, rather than the ra/dec of the source as stored in source attributes of the same name. The former is used in the pairing process, while the latter is generally the optimally weighted mean position from an astrometric solution or other combinatorial process of all individual detection positions across the available passbands. 
y_2Gausig 
[nspid]Source 
WSA NonSurvey 
RMS of axes of ellipse fit in Y_2 
real 
4 
pixels 
0.9999995e9 
MORPH_PARAM 
y_2HallMag 
[nspid]Source 
WSA NonSurvey 
Total point source Y_2 mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_2HallMagErr 
[nspid]Source 
WSA NonSurvey 
Error in total point source Y_2 mag 
real 
4 
mag 
0.9999995e9 
ERROR 
y_2mfID 
[nspid]MergeLog 
WSA NonSurvey 
the UID of the relevant Y_2 multiframe 
bigint 
8 


ID_FRAME 
y_2mhExt 
[nspid]Source 
WSA NonSurvey 
Extended source colour Y_2H (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
y_2mhExtErr 
[nspid]Source 
WSA NonSurvey 
Error on extended source colour Y_2H 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
y_2mhPnt 
[nspid]Source 
WSA NonSurvey 
Point source colour Y_2H (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
y_2mhPntErr 
[nspid]Source 
WSA NonSurvey 
Error on point source colour Y_2H 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
y_2PA 
[nspid]Source 
WSA NonSurvey 
ellipse fit celestial orientation in Y_2 
real 
4 
Degrees 
0.9999995e9 
POS_POSANG 
y_2PetroMag 
[nspid]Source 
WSA NonSurvey 
Extended source Y_2 mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_2PetroMagErr 
[nspid]Source 
WSA NonSurvey 
Error in extended source Y_2 mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_2ppErrBits 
[nspid]Source 
WSA NonSurvey 
additional WFAU postprocessing error bits in Y_2 
int 
4 

0 
CODE_MISC 
Postprocessing 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 4byte 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  All VDFS catalogues  0  6  Bad pixel(s) in default aperture  64  0x00000040  All VDFS catalogues  1  15  Source in poor flat field region  32768  0x00008000  All but mosaics  2  16  Close to saturated  65536  0x00010000  All VDFS catalogues (though deeps excluded prior to DR8)  2  17  Photometric calibration probably subject to systematic error  131072  0x00020000  GPS only  2  19  Possible crosstalk artefact/contamination  524288  0x00080000  All but GPS  2  22  Lies within a dither offset of the stacked frame boundary  4194304  0x00400000  All but mosaics  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. 
y_2PsfMag 
[nspid]Source 
WSA NonSurvey 
Point source profilefitted Y_2 mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_2PsfMagErr 
[nspid]Source 
WSA NonSurvey 
Error in point source profilefitted Y_2 mag 
real 
4 
mag 
0.9999995e9 
ERROR 
y_2SeqNum 
[nspid]Source 
WSA NonSurvey 
the running number of the Y_2 detection 
int 
4 

99999999 
ID_NUMBER 
y_2SerMag2D 
[nspid]Source 
WSA NonSurvey 
Extended source Y_2 mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
y_2SerMag2DErr 
[nspid]Source 
WSA NonSurvey 
Error in extended source Y_2 mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
ERROR 
y_2Xi 
[nspid]Source 
WSA NonSurvey 
Offset of Y_2 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; UHS; also nonsurvey 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. NB: the master position is the position of the detection in the shortest passband in the set, rather than the ra/dec of the source as stored in source attributes of the same name. The former is used in the pairing process, while the latter is generally the optimally weighted mean position from an astrometric solution or other combinatorial process of all individual detection positions across the available passbands. 
yAperMag3 
[nspid]Source 
WSA NonSurvey 
Default point source Y aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yAperMag3 
[nspid]Source 
WSA NonSurvey 
Default point/extended source Y aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yAperMag3Err 
[nspid]Source 
WSA NonSurvey 
Error in default point source Y mag (2.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
yAperMag3Err 
[nspid]Source 
WSA NonSurvey 
Error in default point/extended source Y mag (2.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
yAperMag4 
[nspid]Source 
WSA NonSurvey 
Point source Y aperture corrected mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yAperMag4 
[nspid]Source 
WSA NonSurvey 
Extended source Y aperture corrected mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yAperMag4Err 
[nspid]Source 
WSA NonSurvey 
Error in point source Y mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
yAperMag4Err 
[nspid]Source 
WSA NonSurvey 
Error in extended source Y mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
yAperMag6 
[nspid]Source 
WSA NonSurvey 
Point source Y aperture corrected mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yAperMag6 
[nspid]Source 
WSA NonSurvey 
Extended source Y aperture corrected mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yAperMag6Err 
[nspid]Source 
WSA NonSurvey 
Error in point source Y mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
yAperMag6Err 
[nspid]Source 
WSA NonSurvey 
Error in extended source Y mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
yaStratAst 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Strateva parameter, a, in fit to astrometric rms vs magnitude in Y band, see Sesar et al. 2007. 
real 
4 

0.9999995e9 

The best fit solution to the expected RMS position around the mean for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. 
yaStratPht 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Strateva parameter, a, in fit to photometric rms vs magnitude in Y band, see Sesar et al. 2007. 
real 
4 

0.9999995e9 

The best fit solution to the expected RMS brightness (in magnitudes) for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. This technique was used in Sesar et al. 2007, AJ, 134, 2236. 
ybestAper 
[nspid]Variability 
WSA NonSurvey 
Best aperture (16) for photometric statistics in the Y band 
int 
4 

9999 

Aperture magnitude (16) which gives the lowest RMS for the object. All apertures have the appropriate aperture correction. This can give better values in crowded regions than aperMag3 (see Irwin et al. 2007, MNRAS, 375, 1449) 
ybStratAst 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Strateva parameter, b, in fit to astrometric rms vs magnitude in Y band, see Sesar et al. 2007. 
real 
4 

0.9999995e9 

The best fit solution to the expected RMS position around the mean for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. 
ybStratPht 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Strateva parameter, b, in fit to photometric rms vs magnitude in Y band, see Sesar et al. 2007. 
real 
4 

0.9999995e9 

The best fit solution to the expected RMS brightness (in magnitudes) for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. This technique was used in Sesar et al. 2007, AJ, 134, 2236. 
ychiSqAst 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Goodness of fit of Strateva function to astrometric data in Y band 
real 
4 

0.9999995e9 

The best fit solution to the expected RMS position around the mean for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. 
ychiSqpd 
[nspid]Variability 
WSA NonSurvey 
Chi square (per degree of freedom) fit to data (mean and expected rms) 
real 
4 

0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ychiSqPht 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Goodness of fit of Strateva function to photometric data in Y band 
real 
4 

0.9999995e9 

The best fit solution to the expected RMS brightness (in magnitudes) for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. This technique was used in Sesar et al. 2007, AJ, 134, 2236. 
yClass 
[nspid]Source 
WSA NonSurvey 
discrete image classification flag in Y 
smallint 
2 

9999 
CLASS_MISC 
yClassStat 
[nspid]Source 
WSA NonSurvey 
N(0,1) stellarnessofprofile statistic in Y 
real 
4 

0.9999995e9 
STAT_PROP 
ycStratAst 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Strateva parameter, c, in fit to astrometric rms vs magnitude in Y band, see Sesar et al. 2007. 
real 
4 

0.9999995e9 

The best fit solution to the expected RMS position around the mean for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. 
ycStratPht 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Strateva parameter, c, in fit to photometric rms vs magnitude in Y band, see Sesar et al. 2007. 
real 
4 

0.9999995e9 

The best fit solution to the expected RMS brightness (in magnitudes) for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. This technique was used in Sesar et al. 2007, AJ, 134, 2236. 
yDeblend 
[nspid]Source 
WSA NonSurvey 
placeholder flag indicating parent/child relation in Y 
int 
4 

99999999 
CODE_MISC 
This CASU pipeline processing source extraction flag is a placeholder only, and is always set to zero in all passbands in the merged source lists. If you need to know when a particular image detection is a component of a deblend or not, test bit 4 of attribute ppErrBits (see corresponding glossary entry) which is set by WFAU's postprocessing software based on testing the areal profiles aprof28 (these are set by CASU to 1 for deblended components, or positive values for nondeblended detections). We encode this in an information bit of ppErrBits for convenience when querying the merged source tables. 
yEll 
[nspid]Source 
WSA NonSurvey 
1b/a, where a/b=semimajor/minor axes in Y 
real 
4 

0.9999995e9 
PHYS_ELLIPTICITY 
yeNum 
[nspid]MergeLog 
WSA NonSurvey 
the extension number of this Y frame 
tinyint 
1 


NUMBER 
yErr 
[nspid]Detection 
WSA NonSurvey 
Error in Y coordinate {catalogue TType keyword: Y_coordinate_err} Estimate of centroid error. 
real 
4 
pixels 

ERROR 
yErrBits 
[nspid]Source 
WSA NonSurvey 
processing warning/error bitwise flags in Y 
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. 
yEta 
[nspid]Source 
WSA NonSurvey 
Offset of Y 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; UHS; also nonsurvey 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. NB: the master position is the position of the detection in the shortest passband in the set, rather than the ra/dec of the source as stored in source attributes of the same name. The former is used in the pairing process, while the latter is generally the optimally weighted mean position from an astrometric solution or other combinatorial process of all individual detection positions across the available passbands. 
yexpML 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Expected magnitude limit of frameSet in this in Y band. 
real 
4 

0.9999995e9 

The expected magnitude limit of an intermediate stack, based on the total exposure time. expML=Filter.oneSecML+1.25*log10(totalExpTime). Since different intermediate stacks can have different exposure times, the totalExpTime is the minimum, as long as the number of stacks with this minimum make up 10% of the total. This is a more conservative treatment than just taking the mean or median total exposure time. 
yExpRms 
[nspid]Variability 
WSA NonSurvey 
Rms calculated from polynomial fit to modal RMS as a function of magnitude in Y band 
real 
4 
mag 
0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
yGausig 
[nspid]Source 
WSA NonSurvey 
RMS of axes of ellipse fit in Y 
real 
4 
pixels 
0.9999995e9 
MORPH_PARAM 
yHallMag 
[nspid]Source 
WSA NonSurvey 
Total point source Y mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yHallMagErr 
[nspid]Source 
WSA NonSurvey 
Error in total point source Y mag 
real 
4 
mag 
0.9999995e9 
ERROR 
yIntRms 
[nspid]Variability 
WSA NonSurvey 
Intrinsic rms in Yband 
real 
4 
mag 
0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
yisDefAst 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Use a default model for the astrometric noise in Y band. 
tinyint 
1 

0 

yisDefPht 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Use a default model for the photometric noise in Y band. 
tinyint 
1 

0 

yMagMAD 
[nspid]Variability 
WSA NonSurvey 
Median Absolute Deviation of Y magnitude 
real 
4 
mag 
0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
yMagRms 
[nspid]Variability 
WSA NonSurvey 
rms of Y magnitude 
real 
4 
mag 
0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ymaxCadence 
[nspid]Variability 
WSA NonSurvey 
maximum gap between observations 
real 
4 
days 
0.9999995e9 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
yMaxMag 
[nspid]Variability 
WSA NonSurvey 
Maximum magnitude in Y band, of good detections 
real 
4 

0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ymeanMag 
[nspid]Variability 
WSA NonSurvey 
Mean Y magnitude 
real 
4 
mag 
0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ymedCadence 
[nspid]Variability 
WSA NonSurvey 
median gap between observations 
real 
4 
days 
0.9999995e9 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ymedianMag 
[nspid]Variability 
WSA NonSurvey 
Median Y magnitude 
real 
4 
mag 
0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ymfID 
[nspid]MergeLog 
WSA NonSurvey 
the UID of the relevant Y multiframe 
bigint 
8 


ID_FRAME 
ymhExt 
[nspid]Source 
WSA NonSurvey 
Extended source colour YH (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymhExtErr 
[nspid]Source 
WSA NonSurvey 
Error on extended source colour YH 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymhPnt 
[nspid]Source 
WSA NonSurvey 
Point source colour YH (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymhPntErr 
[nspid]Source 
WSA NonSurvey 
Error on point source colour YH 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
yminCadence 
[nspid]Variability 
WSA NonSurvey 
minimum gap between observations 
real 
4 
days 
0.9999995e9 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
yMinMag 
[nspid]Variability 
WSA NonSurvey 
Minimum magnitude in Y band, of good detections 
real 
4 

0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ymjExt 
[nspid]Source 
WSA NonSurvey 
Extended source colour YJ (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymjExtErr 
[nspid]Source 
WSA NonSurvey 
Error on extended source colour YJ 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymjPnt 
[nspid]Source 
WSA NonSurvey 
Point source colour YJ (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymjPntErr 
[nspid]Source 
WSA NonSurvey 
Error on point source colour YJ 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymkExt 
[nspid]Source 
WSA NonSurvey 
Extended source colour YK (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymkExtErr 
[nspid]Source 
WSA NonSurvey 
Error on extended source colour YK 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymkPnt 
[nspid]Source 
WSA NonSurvey 
Point source colour YK (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
ymkPntErr 
[nspid]Source 
WSA NonSurvey 
Error on point source colour YK 
real 
4 
mag 
0.9999995e9 
ERROR 
Default colours from pairs of adjacent passbands within a given set (e.g. YJ, JH and HK for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the pointsource 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 signaltonoise. At some point in the future, this may be changed such that pointsource colours will be computed from the PSFfitted measures and extended source colours computed from the 2d Sersic model profile fits. 
yndof 
[nspid]Variability 
WSA NonSurvey 
Number of degrees of freedom for chisquare 
smallint 
2 

9999 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ynDofAst 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Number of degrees of freedom of astrometric fit in Y band. 
smallint 
2 

9999 

The best fit solution to the expected RMS position around the mean for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. 
ynDofPht 
[nspid]VarFrameSetInfo 
WSA NonSurvey 
Number of degrees of freedom of photometric fit in Y band. 
smallint 
2 

9999 

The best fit solution to the expected RMS brightness (in magnitudes) for all objects in the frameset. Objects were binned in ranges of magnitude and the median RMS (after clipping out variable objects using the medianabsolute deviation) was calculated. The Strateva function $\zeta(m)>=a+b\,10^{0.4m}+c\,10^{0.8m}$ was fit, where $\zeta(m)$ is the expected RMS as a function of magnitude. The chisquared and number of degrees of freedom are also calculated. This technique was used in Sesar et al. 2007, AJ, 134, 2236. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u05bj1Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u06bh22Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u08a15Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u08bj10Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u09ak1Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u09bd1Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u09bj2Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u09bk1Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u09bk2Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u10a6Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u10ad4Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u10ah99Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u10ak1Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u10ak2Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u10bk1Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u10bk2Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u11ak3Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u11bk1Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u11bk2Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u11bk3Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u11bk4Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u11bk4bDetection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u12ak1Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u12ak2Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u12ak3Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u12ak5Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u12bk3Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u14bua06Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u14bua17Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u15ah02Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u15bh01Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u15bua19Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by u16aua18Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by userv1677Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynFlaggedObs 
[nspid]Variability 
WSA NonSurvey 
Number of detections in Y band flagged as potentially spurious by wserv10Detection.ppErrBits 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
ynGoodObs 
[nspid]Variability 
WSA NonSurvey 
Number of good detections in Y band 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
yNgt3sig 
[nspid]Variability 
WSA NonSurvey 
Number of good detections in Yband that are more than 3 sigma deviations (yAperMagN < (yMeanMag3*yMagRms) 
smallint 
2 

9999 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
yNgt3sig 
[nspid]Variability 
WSA NonSurvey 
Number of good detections in Yband that are more than 3 sigma deviations 
smallint 
2 

9999 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ynMissingObs 
[nspid]Variability 
WSA NonSurvey 
Number of Y band frames that this object should have been detected on and was not 
int 
4 

0 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
yPA 
[nspid]Source 
WSA NonSurvey 
ellipse fit celestial orientation in Y 
real 
4 
Degrees 
0.9999995e9 
POS_POSANG 
yPetroMag 
[nspid]Source 
WSA NonSurvey 
Extended source Y mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yPetroMagErr 
[nspid]Source 
WSA NonSurvey 
Error in extended source Y mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
ERROR 
yPixSize 
[nspid]CurrentAstrometry, [nspid]PreviousAstrometry 
WSA NonSurvey 
Angular size of pixels in Y 
real 
4 
Arcseconds 
0.9999995e9 
pos.angDistance 
yppErrBits 
[nspid]Source 
WSA NonSurvey 
additional WFAU postprocessing error bits in Y 
int 
4 

0 
CODE_MISC 
Postprocessing 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 4byte 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  All VDFS catalogues  0  6  Bad pixel(s) in default aperture  64  0x00000040  All VDFS catalogues  1  15  Source in poor flat field region  32768  0x00008000  All but mosaics  2  16  Close to saturated  65536  0x00010000  All VDFS catalogues (though deeps excluded prior to DR8)  2  17  Photometric calibration probably subject to systematic error  131072  0x00020000  GPS only  2  19  Possible crosstalk artefact/contamination  524288  0x00080000  All but GPS  2  22  Lies within a dither offset of the stacked frame boundary  4194304  0x00400000  All but mosaics  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. 
yprobVar 
[nspid]Variability 
WSA NonSurvey 
Probability of variable from chisquare (and other data) 
real 
4 

0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
yPsfMag 
[nspid]Source 
WSA NonSurvey 
Point source profilefitted Y mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
yPsfMagErr 
[nspid]Source 
WSA NonSurvey 
Error in point source profilefitted Y mag 
real 
4 
mag 
0.9999995e9 
ERROR 
ySeqNum 
[nspid]Source 
WSA NonSurvey 
the running number of the Y detection 
int 
4 

99999999 
ID_NUMBER 
ySerMag2D 
[nspid]Source 
WSA NonSurvey 
Extended source Y mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
ySerMag2DErr 
[nspid]Source 
WSA NonSurvey 
Error in extended source Y mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
ERROR 
ySize 
[nspid]MultiframeDetector 
WSA NonSurvey 
Corresponding image size (Y); value only available if catalogue file exists {catalogue extension keyword: NYOUT} 
int 
4 

99999999 
meta.number 
yskewness 
[nspid]Variability 
WSA NonSurvey 
Skewness in Y band (see Sesar et al. 2007) 
real 
4 

0.9999995e9 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
ytotalPeriod 
[nspid]Variability 
WSA NonSurvey 
total period of observations (last obsfirst obs) 
real 
4 
days 
0.9999995e9 

The observations are classified as good, flagged or missing. Flagged observations are ones where the object has a ppErrBit flag. Missing observations are observations of the part of the sky that include the position of the object, but had no detection. All the statistics are calculated from good observations. The cadence parameters give the minimum, median and maximum time between observations, which is useful to know if the data could be used to find a particular type of variable. 
yVarClass 
[nspid]Variability 
WSA NonSurvey 
Classification of variability in this band 
smallint 
2 

9999 

The photometry is calculated for good observations in the best aperture. The mean, rms, median, median absolute deviation, minMag and maxMag are quite standard. The skewness is calculated as in Sesar et al. 2007, AJ, 134, 2236. The number of good detections that are more than 3 standard deviations can indicate a distribution with many outliers. In each frameset, the mean and rms are used to derive a fit to the expected rms as a function of magnitude. The parameters for the fit are stored in VarFrameSetInfo and the value for the source is in expRms. This is subtracted from the rms in quadrature to get the intrinsic rms: the variability of the object beyond the noise in the system. The chisquared is calculated, assuming a nonvariable object which has the noise from the expectedrms and mean calculated as above. The probVar statistic assumes a chisquared distribution with the correct number of degrees of freedom. The varClass statistic is 1, if the probVar>0.9 and intrinsicRMS/expectedRMS>3. 
yXi 
[nspid]Source 
WSA NonSurvey 
Offset of Y 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; UHS; also nonsurvey 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. NB: the master position is the position of the detection in the shortest passband in the set, rather than the ra/dec of the source as stored in source attributes of the same name. The former is used in the pairing process, while the latter is generally the optimally weighted mean position from an astrometric solution or other combinatorial process of all individual detection positions across the available passbands. 