Home | Overview | Browser | Access | Login | Cookbook | nonSurvey 
  WSA logo

Glossary of WSA attributes

This Glossary alphabetically lists all attributes used in the UKIDSSDR5 database(s) held in the WSA. If you would like to have more information about the schema tables please use the UKIDSSDR5 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
z11 Multiframe WSA 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  
z7 Multiframe WSA 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  
z8 Multiframe WSA 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  
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 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 gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Extended source Z aperture corrected mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 PHOT_MAG
zAperMag4Err gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Error in extended source Z mag (2.8 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR
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 gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Error in extended source Z mag (5.7 arcsec aperture diameter) real 4 mag -0.9999995e9 ERROR
zClass gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource WSA discrete image classification flag in Z smallint 2   -9999 CLASS_MISC
zClassStat gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource WSA N(0,1) stellarness-of-profile statistic in Z real 4   -0.9999995e9 STAT_PROP
zd twomass_scn 2MASS Scan's distance from the zenith at beginning of scan. real 4 degrees   POS_ZD_RES
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 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 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 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 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; 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.
zGausig gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource WSA RMS of axes of ellipse fit in Z real 4 pixels -0.9999995e9 MORPH_PARAM
zHallMag gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Total point source Z mag real 4 mag -0.9999995e9 PHOT_MAG
zHallMagErr gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Error in total point source Z mag real 4 mag -0.9999995e9 ERROR
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
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
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 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 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 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 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.
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 WSATransit default (0) or special (n) zone smallint 2     ID_REGION
zPA gcsPointSource, gcsSource, gcsSourceRemeasurement, gcsZYJHKsource, reliableGcsPointSource WSA ellipse fit celestial orientation in Z real 4 Degrees -0.9999995e9 POS_POS-ANG
zPetroMag gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Extended source Z mag (Petrosian) real 4 mag -0.9999995e9 PHOT_MAG
zPetroMagErr gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Error in extended source Z mag (Petrosian) real 4 mag -0.9999995e9 ERROR
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 LAS, GCS, GPS, DXS
0 6 Bad pixel(s) in default aperture 64 0x00000040 LAS, GCS, GPS, DXS
2 16 Close to saturated 65536 0x00010000 LAS, GCS, GPS
2 19 Possible crosstalk artefact/contamination 524288 0x00080000 LAS, GCS, DXS
2 22 Lies within a dither offset of the stacked frame boundary 4194304 0x00400000 LAS, GCS, GPS, DXS

In this way, the higher the error quality bit flag value, the more likely it is that the detection is spurious. The decimal threshold (column 4) gives the minimum value of the quality flag for a detection having the given condition (since other bits in the flag may be set also; the corresponding hexadecimal value, where each digit corresponds to 4 bits in the flag, can be easier to compute when writing SQL queries to test for a given condition). For example, to exclude all K band sources in the LAS having any error quality condition other than informational ones, include a predicate ... AND kppErrBits ≤ 255. See the SQL Cookbook and other online pages for further information.
zPsfMag gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Point source profile-fitted Z mag real 4 mag -0.9999995e9 PHOT_MAG
zPsfMagErr gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Error in point source profile-fitted Z mag real 4 mag -0.9999995e9 ERROR
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 gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Extended source Z mag (profile-fitted) real 4 mag -0.9999995e9 PHOT_MAG
zSerMag2DErr gcsPointSource, gcsSource, gcsZYJHKsource, reliableGcsPointSource WSA Error in extended source Z mag (profile-fitted) real 4 mag -0.9999995e9 ERROR
ZSOURCE mgcBrightSpec MGC Identifier for best redshift and quality varchar 10      
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; 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.



Home | Overview | Browser | Access | Login | Cookbook | nonSurvey
Listing | Region | MenuQuery | FreeSQL
Links | Credits

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

wsa-support@roe.ac.uk
30/04/2009