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filter u g r i.MP9701 (i) i.MP9702 (y) z
m ab 10.211 9.592 9.343 9.253 9.256 9.241
m bd17 9.769 9.691 9.218 8.914 8.947 8.774
δ ab 0.442 -0.099 0.125 0.339 0.309 0.467
Table 2: Offsets between AB magnitudes and the SNLS Vega-based MegaCam calibration.
It follows that the AB offsets required to bring SNLS magnitudes to AB system, δ ab = m ab − m |x0 , are :
δ ab = −2.5 log 10
∫
λT(λ)φbd17 (λ)dλ
∫
λT(λ)φab (λ)dλ − m bd17 (10)
The pixels in the images are scaled following this relation:
p AB = p VEGA × 10 0.4×δ AB
(11)
3.8 Final catalogue production
In the Wide and Deep surveys, a .ldac SExtractor 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 28, 29 and 30. 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 (Schlegel et al., 1998) 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
Regnault et al. (2009) 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.
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