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Object Catalogues

Catalogue Description

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.

Column Name Type Description
objID* long object ID
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
seeing_flag int seeing flag
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.