Full MGC sample All sources extracted from the imaging data. Apart from real objects like galaxies, stars, QSOs and asteroids, this includes satellite trails, cosmic rays, CCD defects, diffraction spikes and noise detections, including sources fainter than the nominal detection limits. This sample also contains a number of obsoleted "objects". These objects had been considered incorrectly deblended and their catalogue entries were replaced with those from an extraction with different deblending parameter choices. However, the original catalogue entries were retained for completeness and "obsoleted".
    MGC-BRIGHT Those objects from the full sample with extinction-corrected BMGC < 20 mag.
    MGC-FAINT Those objects from the full sample with extinction-corrected BMGC >= 20 mag.
    Clean samples "Clean" objects are those that do not lie in exclusion regions and are brighter than the magnitude limit of the MGC field in which they were detected. In addition, objects from MGC-FAINT must also not lie in MGC fields 14, 15 or 65 which are of sub-standard quality.
    Exclusion regions are areas of the survey where the photometry of objects is likely to be unreliable, e.g. near CCD edges or defects or in the vicinity of very bright stars.
    Spectroscopic samples So far all spectroscopic information in the MGC is limited to MGC-BRIGHT.
    1. The primary goal is to obtain reliable redshifts for all clean galaxies from MGC-BRIGHT. Roughly half of these have redshifts in existing and publically available surveys like the 2dFGRS and SDSS. The remainder form the primary targets for the MGC spectroscopic survey, called MGCz.
    2. The secondary goal is to obtain redshifts for all (real) objects from MGC-BRIGHT, regardless of morphology, in a sub-region of the MGC spanning roughly 2.5 deg in RA.
    3. During the MGCz 2dF observations there were generally more fibres available than primary+secondary targets. The additional fibres were used to observe tertiary targets which comprise:
      1. galaxies in exclusion regions
      2. stellar objects in the outskirts of the stellar locus in colour-colour plots
      3. random stellar objects from the stellar locus
      4. objects where the MGC and SDSS star/galaxy classification disagreed.
      These tertiary samples are in no way complete.
    4. The spectroscopic data we took from the above mentioned public surveys were not limited to clean galaxies from MGC-BRIGHT. Rather we took all available spectroscopic data from these sources, regardless of the corresponding MGC object's classification or other properties. Hence many QSO (candidate) spectra are also found in the MGC.
     

    Joe Liske