Table 2
Selection of SNLS tertiary stars entering the determination of zero-points.
| g | r | i | z | |
|
|
||||
| Magnitude range | 17 <g< 21 | 17.5 <r< 21 | 17.5 <i< 21 | 16.5 <z< 20 |
| Color range | 0.25 <g − i< 2.75 | 0.25 <g − i< 2.75 | 0.25 <g − i< 2.75 | 0.25 <g − i< 2.75 |
| PSF fit qualitya |
|
|
|
|
| Repeatability of aperture fluxb |
|
|
|
|
Notes. Nevertheless, catastrophic χ2 are more likely to be related to measurements affected by undetected saturation which should be discarded. This cut removes about 0.8% of the tertiary stars.
Errors in the PSF model are not taken into account in the computation of the χ2. As a result, for bright stars the χ2 can be large.
The χ2 is built from an accurate model of aperture photometry errors (see B13, Eq. (15)). Large χ2 are related either to variable stars or to problems in the aperture photometry (e.g., apertures with varying contamination).
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