3.8 Final catalogue production
In the Wide and Deep surveys, a .ldacSExtractor source catalogue is produced immediately after the final
rescaling of the stacks (using L99 images for the Wide and the SNLS standard star catalogue for the Deep). The
T0007 Wide and Deep .ldac source catalogues have been produced using a 128 pixels mesh size to
derive the local sky background (BACK_SIZE parameter in SExtractor). These catalogues are the
inputs of the QFITS-out processing. The SExtractor configuration file for the production of the
T0007 .ldac catalogues are presented in Appendix B.2.4 and Appendix A.3.4 for Wide and Deep
respectively.
After the production of the chi2 image, SExtractor is run in dual-image mode on the u*g,r,i,y and z stacks
using the chi2 image as reference. The Wide and Deep chi2 .cat catalogues are produced with a
using a background mesh size in SExtractor of 256 pixels. All catalogues contain parameter
values for all quantities listed in Tables 27, 28 and 29. For each source, aperture magnitudes are
computed within 27 (26+SNLS) apertures, following same procedure as for the previous T0006 release.
The SExtractor configuration file used for the production of the T0007 .cat dual-image mode
catalogues is listed in the Appendix B.2.5 and Appendix A.3.5 for Deep and Wide surveys respectively.
Based on its measured MAG_SNLS, each source is corrected for aperture, leading to the MAG_IQ20
magnitude.
Additionally, for each survey pointing, the following data products are produced:
- a (u, g, r , i∕y, z) Wide or (u, g, r , i,y, z)-merged Deep catalogues that includes a restricted number
of parameters. These catalogues are produced in two versions with either MAG_AUTO, MAG_SNLS
and MAG_IQ20 magnitudes. They also contain the E(B - V) value at each source position derived
from dust map images (?) and the dk cell number for the given position on the image, an estimate
of a second order term of the photometric flatness of the image, meant to account for the slight
variation in bandwidth of the MegaCam filters from center to edge. See ? for a full explanation.
Since it did not bring any significant gain, the dk term is not used within T0007.
- a (u, g, r , i∕y, z)-merged Wide, or (u, g, r, i, y, z)-merged Deep multi-aperture (.ape) extended
catalogue that only includes the data concerning the 27 MAG_APER informations in all filters.
- four (u, g, r , i∕y, z) Wide patch merged catalogues (one for each Wide patch). These catalogues
are produced by matching the objects from the previous multi-aperture merged catalogues in right
ascension and declination. The matching is done across each patch of the Wide with the following
constraints:
- Objects closer than 250 pixels from the tile edges are discarded. This helps removing spurious
objects and is small enough to ensure that the complete area is covered without holes.
- The matching tolerance is set to 1.5 arcsec
- When an object is detected in more than one tile, the object which is kept is the one with the
highest signal to noise ratio (defined as the i-band FLUX_AUTO/FLUXERR_AUTO ratio.)