Z 
Name  Schema Table  Database  Description  Type  Length  Unit  Default Value  Unified Content Descriptor 
z 
allwise_sc2 
WISE 
Unit sphere position z value 
float 
8 



z11 
Multiframe 
WSA 
Spherical: Z11 {image primary HDU keyword: Z11} 
real 
4 

0.9999995e9 

z11 
Multiframe 
WSACalib 
Spherical: Z11 {image primary HDU keyword: Z11} 
real 
4 

0.9999995e9 

z11 
Multiframe 
WSATransit 
Spherical: Z11 {image primary HDU keyword: Z11} 
real 
4 

0.9999995e9 

z11 
Multiframe 
WSAUHS 
Spherical: Z11 {image primary HDU keyword: Z11} 
real 
4 

0.9999995e9 

z7 
Multiframe 
WSA 
Coma: Z7 {image primary HDU keyword: Z7} 
real 
4 

0.9999995e9 

z7 
Multiframe 
WSACalib 
Coma: Z7 {image primary HDU keyword: Z7} 
real 
4 

0.9999995e9 

z7 
Multiframe 
WSATransit 
Coma: Z7 {image primary HDU keyword: Z7} 
real 
4 

0.9999995e9 

z7 
Multiframe 
WSAUHS 
Coma: Z7 {image primary HDU keyword: Z7} 
real 
4 

0.9999995e9 

z8 
Multiframe 
WSA 
Coma: Z8 {image primary HDU keyword: Z8} 
real 
4 

0.9999995e9 

z8 
Multiframe 
WSACalib 
Coma: Z8 {image primary HDU keyword: Z8} 
real 
4 

0.9999995e9 

z8 
Multiframe 
WSATransit 
Coma: Z8 {image primary HDU keyword: Z8} 
real 
4 

0.9999995e9 

z8 
Multiframe 
WSAUHS 
Coma: Z8 {image primary HDU keyword: Z8} 
real 
4 

0.9999995e9 

zAperMag1 
calSynopticSource 
WSACalib 
Extended source Z aperture corrected mag (0.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag1Err 
calSynopticSource 
WSACalib 
Error in extended source Z mag (0.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zAperMag2 
calSynopticSource 
WSACalib 
Extended source Z aperture corrected mag (1.4 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag2Err 
calSynopticSource 
WSACalib 
Error in extended source Z mag (1.4 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zAperMag3 
calSource 
WSACalib 
Default point/extended source Z aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag3 
calSynopticSource 
WSACalib 
Default point/extended source Z aperture corrected mag (2.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag3 
gcsPointSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Default point/extended source Z aperture corrected mag (2.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag3 
gcsSource 
WSA 
Default point/extended source Z aperture corrected mag (2.0 arcsec aperture diameter) If in doubt use this flux estimator 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag3Err 
calSource, calSynopticSource 
WSACalib 
Error in default point/extended source Z mag (2.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zAperMag3Err 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error in default point/extended source Z mag (2.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zAperMag4 
calSource, calSynopticSource 
WSACalib 
Extended source Z aperture corrected mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag4 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Extended source Z aperture corrected mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag4Err 
calSource, calSynopticSource 
WSACalib 
Error in extended source Z mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zAperMag4Err 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error in extended source Z mag (2.8 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zAperMag5 
calSynopticSource 
WSACalib 
Extended source Z aperture corrected mag (4.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag5Err 
calSynopticSource 
WSACalib 
Error in extended source Z mag (4.0 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zAperMag6 
calSource 
WSACalib 
Extended source Z aperture corrected mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag6 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Extended source Z aperture corrected mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zAperMag6Err 
calSource 
WSACalib 
Error in extended source Z mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zAperMag6Err 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error in extended source Z mag (5.7 arcsec aperture diameter) 
real 
4 
mag 
0.9999995e9 
ERROR 
zaStratAst 
calVarFrameSetInfo 
WSACalib 
Strateva parameter, a, in fit to astrometric rms vs magnitude in Z 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. 
zaStratPht 
calVarFrameSetInfo 
WSACalib 
Strateva parameter, a, in fit to photometric rms vs magnitude in Z 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. 
zbestAper 
calVariability 
WSACalib 
Best aperture (16) for photometric statistics in the Z 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) 
zbStratAst 
calVarFrameSetInfo 
WSACalib 
Strateva parameter, b, in fit to astrometric rms vs magnitude in Z 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. 
zbStratPht 
calVarFrameSetInfo 
WSACalib 
Strateva parameter, b, in fit to photometric rms vs magnitude in Z 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. 
zchiSqAst 
calVarFrameSetInfo 
WSACalib 
Goodness of fit of Strateva function to astrometric data in Z 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. 
zchiSqpd 
calVariability 
WSACalib 
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. 
zchiSqPht 
calVarFrameSetInfo 
WSACalib 
Goodness of fit of Strateva function to photometric data in Z 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. 
zClass 
calSource, calSynopticSource 
WSACalib 
discrete image classification flag in Z 
smallint 
2 

9999 
CLASS_MISC 
zClass 
gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource 
WSA 
discrete image classification flag in Z 
smallint 
2 

9999 
CLASS_MISC 
zClassStat 
calSource, calSynopticSource 
WSACalib 
N(0,1) stellarnessofprofile statistic in Z 
real 
4 

0.9999995e9 
STAT_PROP 
zClassStat 
gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource 
WSA 
N(0,1) stellarnessofprofile statistic in Z 
real 
4 

0.9999995e9 
STAT_PROP 
zcStratAst 
calVarFrameSetInfo 
WSACalib 
Strateva parameter, c, in fit to astrometric rms vs magnitude in Z 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. 
zcStratPht 
calVarFrameSetInfo 
WSACalib 
Strateva parameter, c, in fit to photometric rms vs magnitude in Z 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. 
zd 
twomass_scn 
2MASS 
Scan's distance from the zenith at beginning of scan. 
real 
4 
degrees 

POS_ZD_RES 
zd 
twomass_sixx2_scn 
2MASS 
beginning zenith distance of scan data 
real 
4 
deg 


zDeblend 
calSource 
WSACalib 
placeholder flag indicating parent/child relation in Z 
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. 
zDeblend 
calSynopticSource 
WSACalib 
placeholder flag indicating parent/child relation in Z 
int 
4 

99999999 
CODE_MISC 
zDeblend 
gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource 
WSA 
placeholder flag indicating parent/child relation in Z 
int 
4 

99999999 
CODE_MISC 
zDeblend 
gcsSource 
WSA 
placeholder flag indicating parent/child relation in Z 
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. 
zEll 
calSource, calSynopticSource 
WSACalib 
1b/a, where a/b=semimajor/minor axes in Z 
real 
4 

0.9999995e9 
PHYS_ELLIPTICITY 
zEll 
gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource 
WSA 
1b/a, where a/b=semimajor/minor axes in Z 
real 
4 

0.9999995e9 
PHYS_ELLIPTICITY 
zeNum 
calMergeLog, calSynopticMergeLog 
WSACalib 
the extension number of this Z frame 
tinyint 
1 


NUMBER 
zeNum 
gcsMergeLog 
WSA 
the extension number of this Z frame 
tinyint 
1 


NUMBER 
zeNum 
gcsZYJHKmergeLog 
WSA 
the extension number of this frame 
tinyint 
1 


NUMBER 
zErrBits 
calSource, calSynopticSource 
WSACalib 
processing warning/error bitwise flags in Z 
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. 
zErrBits 
gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource 
WSA 
processing warning/error bitwise flags in Z 
int 
4 

99999999 
CODE_MISC 
zErrBits 
gcsSource 
WSA 
processing warning/error bitwise flags in Z 
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. 
zEta 
calSource, calSynopticSource 
WSACalib 
Offset of Z 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. 
zEta 
gcsPointSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Offset of Z detection from master position (+north/south) 
real 
4 
arcsec 
0.9999995e9 
POS_EQ_DEC_OFF 
zEta 
gcsSource 
WSA 
Offset of Z 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. 
zexpML 
calVarFrameSetInfo 
WSACalib 
Expected magnitude limit of frameSet in this in Z 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. 
zExpRms 
calVariability 
WSACalib 
Rms calculated from polynomial fit to modal RMS as a function of magnitude in Z 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. 
zGausig 
calSource, calSynopticSource 
WSACalib 
RMS of axes of ellipse fit in Z 
real 
4 
pixels 
0.9999995e9 
MORPH_PARAM 
zGausig 
gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource 
WSA 
RMS of axes of ellipse fit in Z 
real 
4 
pixels 
0.9999995e9 
MORPH_PARAM 
zHallMag 
calSource 
WSACalib 
Total point source Z mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zHallMag 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Total point source Z mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zHallMagErr 
calSource 
WSACalib 
Error in total point source Z mag 
real 
4 
mag 
0.9999995e9 
ERROR 
zHallMagErr 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error in total point source Z mag 
real 
4 
mag 
0.9999995e9 
ERROR 
zIntRms 
calVariability 
WSACalib 
Intrinsic rms in Zband 
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. 
zisDefAst 
calVarFrameSetInfo 
WSACalib 
Use a default model for the astrometric noise in Z band. 
tinyint 
1 

0 

zisDefPht 
calVarFrameSetInfo 
WSACalib 
Use a default model for the photometric noise in Z band. 
tinyint 
1 

0 

zMag 
gcsSourceRemeasurement 
WSA 
Z mag (as appropriate for this merged source) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zMagErr 
gcsSourceRemeasurement 
WSA 
Error in Z mag 
real 
4 
mag 
0.9999995e9 
ERROR 
zMagMAD 
calVariability 
WSACalib 
Median Absolute Deviation of Z 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. 
zMagRms 
calVariability 
WSACalib 
rms of Z 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. 
zmaxCadence 
calVariability 
WSACalib 
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. 
zMaxMag 
calVariability 
WSACalib 
Maximum magnitude in Z 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. 
zmeanMag 
calVariability 
WSACalib 
Mean Z 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. 
zmedCadence 
calVariability 
WSACalib 
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. 
zmedianMag 
calVariability 
WSACalib 
Median Z 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. 
zmfID 
calMergeLog, calSynopticMergeLog 
WSACalib 
the UID of the relevant Z multiframe 
bigint 
8 


ID_FRAME 
zmfID 
gcsMergeLog 
WSA 
the UID of the relevant Z multiframe 
bigint 
8 


ID_FRAME 
zmfID 
gcsZYJHKmergeLog 
WSA 
the UID of the relevant multiframe 
bigint 
8 


ID_FRAME 
zminCadence 
calVariability 
WSACalib 
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. 
zMinMag 
calVariability 
WSACalib 
Minimum magnitude in Z 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. 
zmy 
gcsSourceRemeasurement 
WSA 
Default colour ZY (using appropriate mags) 
real 
4 
mag 

PHOT_COLOR 
zmyErr 
gcsSourceRemeasurement 
WSA 
Error on colour ZY 
real 
4 
mag 

ERROR 
zmyExt 
calSource 
WSACalib 
Extended source colour ZY (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. 
zmyExt 
gcsPointSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Extended source colour ZY (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
zmyExt 
gcsSource 
WSA 
Extended source colour ZY (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. 
zmyExtErr 
calSource 
WSACalib 
Error on extended source colour ZY 
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. 
zmyExtErr 
gcsPointSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error on extended source colour ZY 
real 
4 
mag 
0.9999995e9 
ERROR 
zmyExtErr 
gcsSource 
WSA 
Error on extended source colour ZY 
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. 
zmyPnt 
calSource, calSynopticSource 
WSACalib 
Point source colour ZY (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. 
zmyPnt 
gcsPointSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Point source colour ZY (using aperMag3) 
real 
4 
mag 
0.9999995e9 
PHOT_COLOR 
zmyPnt 
gcsSource 
WSA 
Point source colour ZY (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. 
zmyPntErr 
calSource, calSynopticSource 
WSACalib 
Error on point source colour ZY 
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. 
zmyPntErr 
gcsPointSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error on point source colour ZY 
real 
4 
mag 
0.9999995e9 
ERROR 
zmyPntErr 
gcsSource 
WSA 
Error on point source colour ZY 
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. 
zndof 
calVariability 
WSACalib 
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. 
znDofAst 
calVarFrameSetInfo 
WSACalib 
Number of degrees of freedom of astrometric fit in Z 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. 
znDofPht 
calVarFrameSetInfo 
WSACalib 
Number of degrees of freedom of photometric fit in Z 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. 
znFlaggedObs 
calVariability 
WSACalib 
Number of detections in Z band flagged as potentially spurious by calDetection.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. 
znGoodObs 
calVariability 
WSACalib 
Number of good detections in Z 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. 
zNgt3sig 
calVariability 
WSACalib 
Number of good detections in Zband 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. 
znMissingObs 
calVariability 
WSACalib 
Number of Z 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. 
zObjID 
gcsPointSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
DEPRECATED (do not use) 
bigint 
8 

99999999 
ID_NUMBER 
zObjID 
gcsSource, gcsSourceRemeasurement 
WSA 
DEPRECATED (do not use) 
bigint 
8 

99999999 
ID_NUMBER 
This attribute is included in source tables for historical reasons, but it's use is not recommended unless you really know what you are doing. In general, if you need to look up detection table attributes for a source in a given passband that are not in the source table, you should make an SQL join between source, mergelog and detection using the primary key attribute frameSetID and combination multiframeID, extNum, seqNum to associate related rows between the three tables. See the Q&A example SQL for more information. 
zone 
ExternalSurveyTable 
WSA 
default (0) or special (n) zone 
smallint 
2 


ID_REGION 
zone 
ExternalSurveyTable 
WSACalib 
default (0) or special (n) zone 
smallint 
2 


ID_REGION 
zone 
ExternalSurveyTable 
WSATransit 
default (0) or special (n) zone 
smallint 
2 


ID_REGION 
zone 
ExternalSurveyTable 
WSAUHS 
default (0) or special (n) zone 
smallint 
2 


ID_REGION 
zPA 
calSource, calSynopticSource 
WSACalib 
ellipse fit celestial orientation in Z 
real 
4 
Degrees 
0.9999995e9 
POS_POSANG 
zPA 
gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource 
WSA 
ellipse fit celestial orientation in Z 
real 
4 
Degrees 
0.9999995e9 
POS_POSANG 
zPetroMag 
calSource 
WSACalib 
Extended source Z mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zPetroMag 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Extended source Z mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zPetroMagErr 
calSource 
WSACalib 
Error in extended source Z mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
ERROR 
zPetroMagErr 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error in extended source Z mag (Petrosian) 
real 
4 
mag 
0.9999995e9 
ERROR 
zppErrBits 
calSource, calSynopticSource 
WSACalib 
additional WFAU postprocessing error bits in Z 
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. 
zppErrBits 
gcsPointSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource 
WSA 
additional WFAU postprocessing error bits in Z 
int 
4 

0 
CODE_MISC 
zppErrBits 
gcsSource 
WSA 
additional WFAU postprocessing error bits in Z 
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. 
zprobVar 
calVariability 
WSACalib 
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. 
zPsfMag 
calSource 
WSACalib 
Point source profilefitted Z mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zPsfMag 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Point source profilefitted Z mag 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zPsfMagErr 
calSource 
WSACalib 
Error in point source profilefitted Z mag 
real 
4 
mag 
0.9999995e9 
ERROR 
zPsfMagErr 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error in point source profilefitted Z mag 
real 
4 
mag 
0.9999995e9 
ERROR 
zSeqNum 
calSource, calSynopticSource 
WSACalib 
the running number of the Z detection 
int 
4 

99999999 
ID_NUMBER 
zSeqNum 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
the running number of the Z detection 
int 
4 

99999999 
ID_NUMBER 
zSeqNum 
gcsSourceRemeasurement 
WSA 
the running number of the Z remeasurement 
int 
4 

99999999 
ID_NUMBER 
zSerMag2D 
calSource 
WSACalib 
Extended source Z mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zSerMag2D 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Extended source Z mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
PHOT_MAG 
zSerMag2DErr 
calSource 
WSACalib 
Error in extended source Z mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
ERROR 
zSerMag2DErr 
gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Error in extended source Z mag (profilefitted) 
real 
4 
mag 
0.9999995e9 
ERROR 
zskewness 
calVariability 
WSACalib 
Skewness in Z 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. 
ZSOURCE 
mgcBrightSpec 
MGC 
Identifier for best redshift and quality 
varchar 
10 



ztotalPeriod 
calVariability 
WSACalib 
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. 
zVarClass 
calVariability 
WSACalib 
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. 
zXi 
calSource, calSynopticSource 
WSACalib 
Offset of Z 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. 
zXi 
gcsPointSource, gcsZYJHKsource, reliableGcsPointSource 
WSA 
Offset of Z detection from master position (+east/west) 
real 
4 
arcsec 
0.9999995e9 
POS_EQ_RA_OFF 
zXi 
gcsSource 
WSA 
Offset of Z 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. 
zyiWS 
calVariability 
WSACalib 
WelchStetson statistic between Z and Y. This assumes colour does not vary much and helps remove variation due to a few poor detections 
real 
4 

0.9999995e9 

The WelchStetson statistic is a measure of the correlation of the variability between two bands. We use the calculation in Welch D.L. and Stetson P.B. 1993, AJ, 105, 5, which is also used in Sesar et al. 2007, AJ, 134, 2236. We use the aperMag3 magnitude when comparing between bands. 