The object catalogue is made available using a relational database system. The FITS catalogues produced by the pipeline processing are converted to ASCII (comma separated values) files for ingestion in a Sybase dataserver. This is accomplished in a two step process. First the single band and band merged catalogues are read and one ASCII file per database table in the database is written to disk. This is done in a per run basis. In a second stage the ASCII tables are ingested in the database and proper indexes created.
We have followed the philosophy of reducing the number of tables presented to the user as much as possible. The database contains four tables which are summarised below.
- FieldsAll. Information about the field centres and number of objects detected.
- ChipsAll. This table contains parameters about the observation (airmass, exposure time, World Coordinate System) as well as the Data Quality Control attributes for each chip, i.e, mean seeing and ellipticity, zero point, sky level, etc.
- PhotoObj. Main catalogue containing all detections with image derived parameters and calibrated magnitudes.
- PhotoObjBest. Subset of PhotoObj with only objects detected in the three bands in seeing conditions better than 2.0 arcsec. Additional constraints are used to select only those observation in good photometric conditions and thus will vary little between the EDR and the Final Data Release. At this effect only nights for which the overall magnitude zero point rms in the r' band is better than 4% are included in this catalogue.
The following table lists the columns, types and description of the PhotoObjBest catalogue. Columns marked with an asterisk (*) are indexed so queries performed using those columns will run faster.
NOTE: All magnitudes in the catalogues are in the Vega system.
|ra*||float||R.A. in degrees (deg, J2000)|
|dec*||float||Dec in degrees (deg, J2000)|
|glon||float||Galactic longitude (deg)|
|glat||float||Galactic latitude (deg)|
|coremag_r||float||r' aperture corrected magnitude|
|coremag_i||float||i' aperture corrected magnitude|
|coremag_ha||float||Ha aperture corrected magnitude|
|coremagerr_r||float||r' magnitude error|
|coremagerr_i||float||i' magnitude error|
|coremagerr_ha||float||Ha magnitude error|
|class_r||int||r' star/galaxy clasification index|
|class_i||int||i' star/galaxy clasification index|
|class_ha||int||Ha star/galaxy clasification index|
|ellipt_r||real||ellipticity as measured in r'|
|ellipt_i||real||ellipticity as measured in i'|
|ellipt_ha||real||ellipticity as measured in Ha|
|posang_r||real||position angle as measured in r'|
|posang_i||real||position angle as measured in i'|
|posang_ha||real||position angle as measured in Ha|
|photom_flagf||int||zero if object detected in all bands|
|class_flag||int||combined probabily of stellar object|
|chip_r_id*||long||link to r' chip table|
|chip_i_id*||long||link to i' chip table|
|chip_ha_id*||long||link to Ha chip table|
|cxf||float||Spherical coordinate x|
|cyf||float||Spherical coordinate y|
|czf||float||Spherical coordinate z|
|field_id*||long||link to field table|
List of Best fields
A list of all fields included in the catalogue of best observations PhotoObjBest is available here.