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Glossary of WSA attributes

This Glossary alphabetically lists all attributes used in the UKIDSSDR10 database(s) held in the WSA. If you would like to have more information about the schema tables please use the UKIDSSDR10 Schema Browser (other Browser versions).
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z

Z

NameSchema TableDatabaseDescriptionTypeLengthUnitDefault ValueUnified 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 median-absolute 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 chi-squared 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 median-absolute 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 chi-squared 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 (1-6) for photometric statistics in the Z band int 4   -9999  
Aperture magnitude (1-6) 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 median-absolute 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 chi-squared 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 median-absolute 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 chi-squared 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 median-absolute 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 chi-squared 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 median-absolute 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 chi-squared 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) stellarness-of-profile statistic in Z real 4   -0.9999995e9 STAT_PROP
zClassStat gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource WSA N(0,1) stellarness-of-profile 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 median-absolute 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 chi-squared 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 median-absolute 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 chi-squared 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 post-processing software based on testing the areal profiles aprof2-8 (these are set by CASU to -1 for deblended components, or positive values for non-deblended 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 post-processing software based on testing the areal profiles aprof2-8 (these are set by CASU to -1 for deblended components, or positive values for non-deblended detections). We encode this in an information bit of ppErrBits for convenience when querying the merged source tables.
zEll calSource, calSynopticSource WSACalib 1-b/a, where a/b=semi-major/minor axes in Z real 4   -0.9999995e9 PHYS_ELLIPTICITY
zEll gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource WSA 1-b/a, where a/b=semi-major/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 non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want. 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 non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want. 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 Z-Y (using appropriate mags) real 4 mag   PHOT_COLOR
zmyErr gcsSourceRemeasurement WSA Error on colour Z-Y real 4 mag   ERROR
zmyExt calSource WSACalib Extended source colour Z-Y (using aperMag3) real 4 mag -0.9999995e9 PHOT_COLOR
Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
zmyExt gcsPointSource, gcsZYJHKsource, reliableGcsPointSource WSA Extended source colour Z-Y (using aperMag3) real 4 mag -0.9999995e9 PHOT_COLOR
zmyExt gcsSource WSA Extended source colour Z-Y (using aperMag3) real 4 mag -0.9999995e9 PHOT_COLOR
Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
zmyExtErr calSource WSACalib Error on extended source colour Z-Y real 4 mag -0.9999995e9 ERROR
Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
zmyExtErr gcsPointSource, gcsZYJHKsource, reliableGcsPointSource WSA Error on extended source colour Z-Y real 4 mag -0.9999995e9 ERROR
zmyExtErr gcsSource WSA Error on extended source colour Z-Y real 4 mag -0.9999995e9 ERROR
Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
zmyPnt calSource, calSynopticSource WSACalib Point source colour Z-Y (using aperMag3) real 4 mag -0.9999995e9 PHOT_COLOR
Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
zmyPnt gcsPointSource, gcsZYJHKsource, reliableGcsPointSource WSA Point source colour Z-Y (using aperMag3) real 4 mag -0.9999995e9 PHOT_COLOR
zmyPnt gcsSource WSA Point source colour Z-Y (using aperMag3) real 4 mag -0.9999995e9 PHOT_COLOR
Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
zmyPntErr calSource, calSynopticSource WSACalib Error on point source colour Z-Y real 4 mag -0.9999995e9 ERROR
Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
zmyPntErr gcsPointSource, gcsZYJHKsource, reliableGcsPointSource WSA Error on point source colour Z-Y real 4 mag -0.9999995e9 ERROR
zmyPntErr gcsSource WSA Error on point source colour Z-Y real 4 mag -0.9999995e9 ERROR
Default colours from pairs of adjacent passbands within a given set (e.g. Y-J, J-H and H-K for YJHK) are recorded in the merged source table for ease of querying and speedy querying via indexing of these attributes. Presently, the point-source colours and extended source colours are computed from the aperture corrected AperMag3 fixed 2 arcsec aperture diameter measures (for consistent measurement across all passbands) and generally good signal-to-noise. At some point in the future, this may be changed such that point-source colours will be computed from the PSF-fitted measures and extended source colours computed from the 2-d Sersic model profile fits.
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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 median-absolute 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 chi-squared 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 median-absolute 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 chi-squared 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 Z-band 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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_POS-ANG
zPA gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource WSA ellipse fit celestial orientation in Z real 4 Degrees -0.9999995e9 POS_POS-ANG
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 post-processing error bits in Z int 4   0 CODE_MISC
Post-processing error quality bit flags assigned (NB: from UKIDSS DR2 release onwards) in the WSA curation procedure for survey data. From least to most significant byte in the 4-byte integer attribute byte 0 (bits 0 to 7) corresponds to information on generally innocuous conditions that are nonetheless potentially significant as regards the integrity of that detection; byte 1 (bits 8 to 15) corresponds to warnings; byte 2 (bits 16 to 23) corresponds to important warnings; and finally byte 3 (bits 24 to 31) corresponds to severe warnings:
ByteBitDetection quality issue Threshold or bit mask Applies to
DecimalHexadecimal
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 post-processing error bits in Z int 4   0 CODE_MISC
zppErrBits gcsSource WSA additional WFAU post-processing error bits in Z int 4   0 CODE_MISC
Post-processing error quality bit flags assigned (NB: from UKIDSS DR2 release onwards) in the WSA curation procedure for survey data. From least to most significant byte in the 4-byte integer attribute byte 0 (bits 0 to 7) corresponds to information on generally innocuous conditions that are nonetheless potentially significant as regards the integrity of that detection; byte 1 (bits 8 to 15) corresponds to warnings; byte 2 (bits 16 to 23) corresponds to important warnings; and finally byte 3 (bits 24 to 31) corresponds to severe warnings:
ByteBitDetection quality issue Threshold or bit mask Applies to
DecimalHexadecimal
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 chi-square (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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 profile-fitted Z mag real 4 mag -0.9999995e9 PHOT_MAG
zPsfMag gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Point source profile-fitted Z mag real 4 mag -0.9999995e9 PHOT_MAG
zPsfMagErr calSource WSACalib Error in point source profile-fitted Z mag real 4 mag -0.9999995e9 ERROR
zPsfMagErr gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Error in point source profile-fitted 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 (profile-fitted) real 4 mag -0.9999995e9 PHOT_MAG
zSerMag2D gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Extended source Z mag (profile-fitted) real 4 mag -0.9999995e9 PHOT_MAG
zSerMag2DErr calSource WSACalib Error in extended source Z mag (profile-fitted) real 4 mag -0.9999995e9 ERROR
zSerMag2DErr gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Error in extended source Z mag (profile-fitted) 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 obs-first 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 chi-squared is calculated, assuming a non-variable object which has the noise from the expected-rms and mean calculated as above. The probVar statistic assumes a chi-squared 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 non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want. 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 non-survey programmes) or 1.0 (UKIDSS GPS, DXS and UDS) arcseconds is used, the higher value enabling pairing of moving sources when epoch separations may be several years. Such a large association criterion can of course lead to spurious pairings in the merged sources lists (although note that between passband pairs, handshake pairing is done: both passbands must agree that the candidate pair is their nearest neighbour for the pair to propagate through into the merged source table). In order to help filter spurious pairings out, and assuming that large positional offsets between the different passband detections are not expected (e.g. because of source motion, or larger than usual positional uncertainties) then the attributes Xi and Eta can be used to filter any pairings with suspiciously large offsets in one or more bands. For example, for a clean sample of QSOs from the LAS, you might wish to insist that the offsets in the selected sample are all below 1 arcsecond: simply add WHERE clauses into the SQL sample selection script to exclude all Xi and Eta values larger than the threshold you want. 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 Welch-Stetson 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 Welch-Stetson 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.



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19/04/2018