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Glossary of VULCAN attributes

This Glossary alphabetically lists all attributes used in the VULCANv20260525 database(s) held in the ASNIR. If you would like to have more information about the schema tables please use the VULCANv20260525 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

Y

NameSchema TableDatabaseDescriptionTypeLengthUnitDefault ValueUnified Content Descriptor
y allwise_sc WISE Unit sphere position y value float 8      
y_coadd twomass_xsc TWOMASS y (in-scan) position (coadd coord.). real 4 arcsec   pos.cartesian;instr.det
yABMagLim allSkyNIRFrameSetInfo VULCANiDR AB magnitude limit of pointing in J band float 8 mag    
yAllAperMag3 allSkyNIRSource VULCANiDR Default point source Y aperture corrected mag (2.0 arcsec aperture diameter) using All Sky calibration
If in doubt use this flux estimator		 real 4 mag -0.9999995e9 phot.mag&MagUCD&
yAllAperMag3Err allSkyNIRSource VULCANiDR Error in default point/extended source Y mag (2.0 arcsec aperture diameter) using All Sky calibration real 4 mag -0.9999995e9 stat.error;phot.mag&MagUCD&
yAllAperMag4 allSkyNIRSource VULCANiDR Point source Y aperture corrected mag (2.8 arcsec aperture diameter) using All Sky calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yAllAperMag4Err allSkyNIRSource VULCANiDR Error in point/extended source Y mag (2.8 arcsec aperture diameter) using All Sky calibration real 4 mag -0.9999995e9 stat.error;phot.mag&MagUCD&
yAllAperMag6 allSkyNIRSource VULCANiDR Point source Y aperture corrected mag (5.7 arcsec aperture diameter) using All Sky calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yAllAperMag6Err allSkyNIRSource VULCANiDR Error in point/extended source Y mag (5.7 arcsec aperture diameter) using All Sky calibration real 4 mag -0.9999995e9 stat.error;phot.mag&MagUCD&
yAllAperMagNoAperCorr3 allSkyNIRSource VULCANiDR Default extended source Y aperture mag (2.0 arcsec aperture diameter) using All Sky calibration
If in doubt use this flux estimator		 real 4 mag -0.9999995e9 phot.mag&MagUCD&
yAllAperMagNoAperCorr4 allSkyNIRSource VULCANiDR Extended source Y aperture mag (2.8 arcsec aperture diameter) using All Sky calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yAllAperMagNoAperCorr6 allSkyNIRSource VULCANiDR Extended source Y aperture mag (5.7 arcsec aperture diameter) using All Sky calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yAllPetroMag allSkyNIRSource VULCANiDR Extended source Y mag (Petrosian) using All Sky calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yAllPetroMagErr allSkyNIRSource VULCANiDR Error in extended source Y mag (Petrosian) using All Sky calibration real 4 mag -0.9999995e9 stat.error;phot.mag&MagUCD&
yApFillFac StackObjectAttributes PS1DR2 Aperture fill factor from y filter stack detection. real 4   -999  
yApFlux StackObjectAttributes PS1DR2 Aperture flux from y filter stack detection. real 4 Janskys -999  
yApFluxErr StackObjectAttributes PS1DR2 Error in aperture flux from y filter stack detection. real 4 Janskys -999  
yApMag StackObjectThin PS1DR2 Aperture magnitude from y filter stack detection. real 4 AB magnitudes -999  
yApMagErr StackObjectThin PS1DR2 Error in aperture magnitude from y filter stack detection. real 4 AB magnitudes -999  
yApRadius StackObjectAttributes PS1DR2 Aperture radius for y filter stack detection. real 4 arcsec -999  
yClass allSkyNIRSource VULCANiDR discrete image classification flag in Y smallint 2   -9999 src.class&MagUCD&
yClassStat allSkyNIRSource VULCANiDR N(0,1) stellarness-of-profile statistic/SExtractor STAR_CLASS in Y real 4   -0.9999995e9 stat&MagUCD&
ydec StackObjectThin PS1DR2 Declination from y filter stack detection. float 8 degrees -999  
ydecErr StackObjectThin PS1DR2 Declination error from y filter stack detection. real 4 arcsec -999  
yEll allSkyNIRSource VULCANiDR 1-b/a, where a/b=semi-major/minor axes in Y real 4   -0.9999995e9 src.ellipticity&MagUCD&
yeNum allSkyNIRFrameSetInfo VULCANiDR the extension number of this Y frame tinyint 1     meta.number;em.IR.K
yEpoch StackObjectThin PS1DR2 Modified Julian Date of the mean epoch of images contributing to the the y-band stack (equinox J2000). float 8 days -999  
yErrBits allSkyNIRSource VULCANiDR processing warning/error bitwise flags in Y int 4   -99999999 meta.code&MagUCD&
Apparently not actually an error bit flag, but a count of the number of zero confidence pixels in the default (2 arcsec diameter) aperture.
yEta allSkyNIRSource VULCANiDR Offset of Y detection from master position (+north/-south) real 4 arcsec -0.9999995e9 pos.eq.dec;arith.diff&MagUCD&
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.
yexpTime StackObjectAttributes PS1DR2 Exposure time of the y filter stack. Necessary for converting listed fluxes and magnitudes back to measured ADU counts. real 4 seconds -999  
yExtNSigma StackObjectAttributes PS1DR2 An extendedness measure for the y filter stack detection based on the deviation between PSF and Kron (1980) magnitudes, normalized by the PSF magnitude uncertainty. real 4   -999  
yFlags MeanObject PS1DR2 Information flag bitmask for mean object from y filter detections. Values listed in ObjectFilterFlags. int 4   0  
yGausig allSkyNIRSource VULCANiDR RMS of axes of ellipse fit in Y real 4 pixels -0.9999995e9 src.morph.param&MagUCD&
yHlCorSMjRadAs allSkyNIRSource VULCANiDR Seeing corrected half-light, semi-major axis in Y band real 4 arcsec -0.9999995e9 phys.angSize;em.opt.I
yinfoFlag StackObjectThin PS1DR2 Information flag bitmask indicating details of the y filter stack photometry. Values listed in DetectionFlags. bigint 8   0  
yinfoFlag2 StackObjectThin PS1DR2 Information flag bitmask indicating details of the y filter stack photometry. Values listed in DetectionFlags2. int 4   0  
yinfoFlag3 StackObjectThin PS1DR2 Information flag bitmask indicating details of the y filter stack photometry. Values listed in DetectionFlags3. int 4   0  
yippDetectID StackObjectAttributes, StackObjectThin PS1DR2 IPP internal detection identifier. bigint 8      
yKronFlux StackObjectAttributes PS1DR2 Kron (1980) flux from y filter stack detection. real 4 Janskys -999  
yKronFluxErr StackObjectAttributes PS1DR2 Error in Kron (1980) flux from y filter stack detection. real 4 Janskys -999  
yKronMag StackObjectThin PS1DR2 Kron (1980) magnitude from y filter stack detection. real 4 AB magnitudes -999  
yKronMagErr StackObjectThin PS1DR2 Error in Kron (1980) magnitude from y filter stack detection. real 4 AB magnitudes -999  
yKronRad StackObjectAttributes PS1DR2 Kron (1980) radius from y filter stack detection. real 4 arcsec -999  
yMeanApMag MeanObject PS1DR2 Mean aperture magnitude from y filter detections. real 4 AB magnitudes -999  
yMeanApMagErr MeanObject PS1DR2 Error in mean aperture magnitude from y filter detections. real 4 AB magnitudes -999  
yMeanApMagNpt MeanObject PS1DR2 Number of measurements included in mean aperture magnitude from y filter detections. smallint 2   -999  
yMeanApMagStd MeanObject PS1DR2 Standard deviation of aperture magnitudes from y filter detections. real 4 AB magnitudes -999  
yMeanKronMag MeanObject PS1DR2 Mean Kron (1980) magnitude from y filter detections. real 4 AB magnitudes -999  
yMeanKronMagErr MeanObject PS1DR2 Error in mean Kron (1980) magnitude from y filter detections. real 4 AB magnitudes -999  
yMeanKronMagNpt MeanObject PS1DR2 Number of measurements included in mean Kron (1980) magnitude from y filter detections. smallint 2   -999  
yMeanKronMagStd MeanObject PS1DR2 Standard deviation of Kron (1980) magnitudes from y filter detections. real 4 AB magnitudes -999  
yMeanPSFMag MeanObject PS1DR2 Mean PSF magnitude from y filter detections. real 4 AB magnitudes -999  
yMeanPSFMagErr MeanObject PS1DR2 Error in mean PSF magnitude from y filter detections. real 4 AB magnitudes -999  
yMeanPSFMagMax MeanObject PS1DR2 Maximum PSF magnitude from y filter detections. real 4 AB magnitudes -999  
yMeanPSFMagMin MeanObject PS1DR2 Minimum PSF magnitude from y filter detections. real 4 AB magnitudes -999  
yMeanPSFMagNpt MeanObject PS1DR2 Number of measurements included in mean PSF magnitude from y filter detections. smallint 2   -999  
yMeanPSFMagStd MeanObject PS1DR2 Standard deviation of PSF magnitudes from y filter detections. real 4 AB magnitudes -999  
ymfID allSkyNIRFrameSetInfo VULCANiDR the UID of the relevant Y multiframe bigint 8     meta.id;obs.field;em.IR.K
ymjAllExt allSkyNIRSource VULCANiDR Extended source colour Y-J (using aperMagNoAperCorr3) for All Sky calibration real 4 mag -0.9999995e9 phot.color&ColorUCD&
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.
ymjAllExtErr allSkyNIRSource VULCANiDR Error on extended source colour Y-J for All Sky calibration real 4 mag -0.9999995e9 stat.error&ColorUCD&
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.
ymjAllPnt allSkyNIRSource VULCANiDR Point source colour Y-J (using aperMag3) for All Sky calibration real 4 mag -0.9999995e9 phot.color&ColorUCD&
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.
ymjAllPntErr allSkyNIRSource VULCANiDR Error on point source colour Y-J for All Sky calibration real 4 mag -0.9999995e9 stat.error&ColorUCD&
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.
yMjd allSkyNIRSource VULCANiDR Modified Julian Day in Y band float 8 days -0.9999995e9 time.epoch&MagUCD&
ymjTelExt allSkyNIRSource VULCANiDR Extended source colour Y-J (using aperMagNoAperCorr3) for original calibration real 4 mag -0.9999995e9 phot.color&ColorUCD&
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.
ymjTelExtErr allSkyNIRSource VULCANiDR Error on extended source colour Y-J for original calibration real 4 mag -0.9999995e9 stat.error&ColorUCD&
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.
ymjTelPnt allSkyNIRSource VULCANiDR Point source colour Y-J (using aperMag3) for original calibration real 4 mag -0.9999995e9 phot.color&ColorUCD&
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.
ymjTelPntErr allSkyNIRSource VULCANiDR Error on point source colour Y-J for original calibration real 4 mag -0.9999995e9 stat.error&ColorUCD&
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.
ymomentR1 StackObjectAttributes PS1DR2 First radial moment for y filter stack detection. real 4 arcsec -999  
ymomentRH StackObjectAttributes PS1DR2 Half radial moment (r^0.5 weighting) for y filter stack detection. real 4 arcsec^0.5 -999  
ymomentXX StackObjectAttributes PS1DR2 Second moment M_xx for y filter stack detection. real 4 arcsec^2 -999  
ymomentXY StackObjectAttributes PS1DR2 Second moment M_xy for y filter stack detection. real 4 arcsec^2 -999  
ymomentYY StackObjectAttributes PS1DR2 Second moment M_yy for y filter stack detection. real 4 arcsec^2 -999  
yNEpochs allSkyNIRFrameSetInfo VULCANiDR Number of epochs in Y band (0 if no measurements) int 4      
ynFrames StackObjectThin PS1DR2 Number of input frames/exposures contributing to the y filter stack detection. int 4   -999  
yObs allSkyNIRSource VULCANiDR There are pixels at this position in the Y-band tinyint 1   0 meta.flag
yPA allSkyNIRSource VULCANiDR ellipse fit celestial orientation in Y real 4 Degrees -0.9999995e9 pos.posAng&MagUCD&
yPixSize CurrentAstrometry VULCANiDR Angular size of pixels in Y real 4 Arcseconds -0.9999995e9 pos.angDistance
yPlateScale StackObjectAttributes PS1DR2 Local plate scale for the y filter stack. real 4 arcsec/pixel 0  
yPos Detection PS1DR2 PSF y center location. real 4 raw pixels -999  
yPosErr Detection PS1DR2 Error in PSF y center location. real 4 raw pixels -999  
yppErrBits allSkyNIRSource VULCANiDR additional WFAU post-processing error bits in Y int 4   0 meta.code&MagUCD&
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.
ypsfChiSq StackObjectAttributes PS1DR2 Reduced chi squared value of the PSF model fit for y filter stack detection. real 4   -999  
ypsfCore StackObjectAttributes PS1DR2 PSF core parameter k from y filter stack detection, where F = F0 / (1 + k r^2 + r^3.33). real 4   -999  
yPSFFlux StackObjectAttributes PS1DR2 PSF flux from y filter stack detection. real 4 Janskys -999  
yPSFFluxErr StackObjectAttributes PS1DR2 Error in PSF flux from y filter stack detection. real 4 Janskys -999  
ypsfLikelihood StackObjectAttributes PS1DR2 Likelihood that this y filter stack detection is best fit by a PSF. real 4   -999  
yPSFMag StackObjectThin PS1DR2 PSF magnitude from y filter stack detection. real 4 AB magnitudes -999  
yPSFMagErr StackObjectThin PS1DR2 Error in PSF magnitude from y filter stack detection. real 4 AB magnitudes -999  
ypsfMajorFWHM StackObjectAttributes PS1DR2 PSF major axis FWHM from y filter stack detection. real 4 arcsec -999  
ypsfMinorFWHM StackObjectAttributes PS1DR2 PSF minor axis FWHM from y filter stack detection. real 4 arcsec -999  
ypsfQf StackObjectAttributes PS1DR2 PSF coverage factor for y filter stack detection. real 4   -999  
ypsfQfPerfect StackObjectAttributes PS1DR2 PSF-weighted fraction of pixels totally unmasked for y filter stack detection. real 4   -999  
ypsfTheta StackObjectAttributes PS1DR2 PSF major axis orientation from y filter stack detection. real 4 degrees -999  
yQfPerfect MeanObject PS1DR2 Maximum PSF weighted fraction of pixels totally unmasked from y filter detections. real 4   -999  
yra StackObjectThin PS1DR2 Right ascension from y filter stack detection. float 8 degrees -999  
yraErr StackObjectThin PS1DR2 Right ascension error from y filter stack detection. real 4 arcsec -999  
ySeeing allSkyNIRFrameSetInfo VULCANiDR Y band seeing float 8 arcsec    
ySeqNum allSkyNIRSource VULCANiDR the running number of the Y detection int 4   -99999999 meta.number&MagUCD&
ysky StackObjectAttributes PS1DR2 Residual background sky level at the y filter stack detection. real 4 Janskys/arcsec^2 -999  
yskyErr StackObjectAttributes PS1DR2 Error in residual background sky level at the y filter stack detection. real 4 Janskys/arcsec^2 -999  
ystackDetectID StackObjectAttributes, StackObjectThin PS1DR2 Unique stack detection identifier. bigint 8      
ystackImageID StackObjectAttributes, StackObjectThin PS1DR2 Unique stack identifier for y filter detection. bigint 8      
yTelAperMag3 allSkyNIRSource VULCANiDR Default point source Y aperture corrected mag (2.0 arcsec aperture diameter) using original calibration
If in doubt use this flux estimator		 real 4 mag -0.9999995e9 phot.mag&MagUCD&
yTelAperMag3Err allSkyNIRSource VULCANiDR Error in default point/extended source Y mag (2.0 arcsec aperture diameter) using original calibration real 4 mag -0.9999995e9 stat.error;phot.mag&MagUCD&
yTelAperMag4 allSkyNIRSource VULCANiDR Point source Y aperture corrected mag (2.8 arcsec aperture diameter) using original calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yTelAperMag4Err allSkyNIRSource VULCANiDR Error in point/extended source Y mag (2.8 arcsec aperture diameter) using original calibration real 4 mag -0.9999995e9 stat.error;phot.mag&MagUCD&
yTelAperMag6 allSkyNIRSource VULCANiDR Point source Y aperture corrected mag (5.7 arcsec aperture diameter) using original calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yTelAperMag6Err allSkyNIRSource VULCANiDR Error in point/extended source Y mag (5.7 arcsec aperture diameter) using original calibration real 4 mag -0.9999995e9 stat.error;phot.mag&MagUCD&
yTelAperMagNoAperCorr3 allSkyNIRSource VULCANiDR Default extended source Y aperture mag (2.0 arcsec aperture diameter) using original calibration
If in doubt use this flux estimator		 real 4 mag -0.9999995e9 phot.mag&MagUCD&
yTelAperMagNoAperCorr4 allSkyNIRSource VULCANiDR Extended source Y aperture mag (2.8 arcsec aperture diameter) using original calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yTelAperMagNoAperCorr6 allSkyNIRSource VULCANiDR Extended source Y aperture mag (5.7 arcsec aperture diameter) using original calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yTelPetroMag allSkyNIRSource VULCANiDR Extended source Y mag (Petrosian) using original calibration real 4 mag -0.9999995e9 phot.mag&MagUCD&
yTelPetroMagErr allSkyNIRSource VULCANiDR Error in extended source Y mag (Petrosian) using original calibration real 4 mag -0.9999995e9 stat.error;phot.mag&MagUCD&
yXi allSkyNIRSource VULCANiDR Offset of Y detection from master position (+east/-west) real 4 arcsec -0.9999995e9 pos.eq.ra;arith.diff&MagUCD&
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.
yxPos StackObjectAttributes PS1DR2 PSF x center location from y filter stack detection. real 4 sky pixels -999  
yxPosErr StackObjectAttributes PS1DR2 Error in PSF x center location from y filter stack detection. real 4 sky pixels -999  
yyPos StackObjectAttributes PS1DR2 PSF y center location from y filter stack detection. real 4 sky pixels -999  
yyPosErr StackObjectAttributes PS1DR2 Error in PSF y center location from y filter stack detection. real 4 sky pixels -999  
yzp StackObjectAttributes PS1DR2 Photometric zeropoint for the y filter stack. Necessary for converting listed fluxes and magnitudes back to measured ADU counts. real 4 magnitudes 0  


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25/05/2026