4.6 Outliers, stacks with exceptions or anomalies

Several images show unusual properties with respect to the bulk sample of stacks. This is the case for the 32 y-band stacks that are expected to have slightly different (photometric) properties compared to the other 139 i-band tiles due to the slightly different bandwidth of that replacement filter after the original one broke in 2007.

The most common technical anomaly is an amplifier failure during an observing sequence. Since all CCDs have two outputs, several images show missing data from a half or a full CCD area. Usually, each observing sequence is done only once, so the data from the missing CCD cannot be recovered. However, since the CCD failures are intermittent, the r-band observations which have been split into two observing sequences normally do not experience this missing data problem. We note furthermore that many of the pointings originally affected by this problem have been re-observed by in Director’s Discretionary Time (images with more than one full CCD missing have been rejected during the image selection stack.)

Problematic T0007 stacks are listed in Tables 14 and 15, with a short description. None of these problems are critical for the scientific exploitation of the survey, but there are some half-CCD size regions of the CFHTLS Wide where one or two filters are missing.







W Cartesian CFHTLS Special filter VIPERS-DDT images

Comments

Ident name Ident name






W1(-4 - 4) 020241-104400 y-band observations

y-band exp. time is 7380 s.
W1(-3 -4) 020631-104400 y-band observations

W1(-2 -0) 021021-070000

radial astrometric offset around 0.090" in all bands

W1(-2 -4) 021021-104400 y-band observations

W1(+2 -0) 022539-070000

g-band: CCD#03 missing

W1(+2 + 1) 022539-060400 y-band observations y-band

W1(+2 + 2) 022539-050800 y-band observations u*-band

W1(+2 + 3) 022539-041200

u*-band and z-band: CCD#03 missing    ;    

W1(-1 -4) 021410-104400 y-band observations

W1(-0 -4) 021800-104400 y-band observations

W1(+1 -4) 022150-104400 y-band observations

W1(+1 -1) 022150-075600 y-band observations

W1(+1 + 1) 022150-060400 y-band observations

W1(+1 + 3) 022150-041200

i-band : two 1/2 CCD missing (CCD#07 and CCD#11)

u*-band radial astrometric offset 0.084"

W1(+2 - 4) 022539-104400 y-band observations

W1(+3 -4) 022929-104400 y-band observations

W1(+3 -0) 022929-070000

g-band and i-band : CCD#03 missing    ;    

W1(+3 + 1) 022929-060400 y-band observations g-band

W1(+3 + 2) 022929-050800 y-band observations g-band, y-band

W1(+3 + 3) 022929-041200

g-band and i-band : CCD#03 missing

W1(+4 -4) 023319-104400 y-band observations

W1(+4 -0) 023319-070000

g-band and i-band : CCD#03 missing    ;    u,gand i-band radial astrometric around 0.079"







Table 14: CFHTLS Wide stacks with exceptions or anomalies.







W Cartesian CFHTLS Special filter VIPERS-DDT images

Comments

Ident name Ident name






W1(+4 + 1) 023319-060400 g-band

W1(+4 + 2) 023319-050800 y-band observations g-band

W1(+4 + 3) 023319-041200

i-band : CCD#03 missing

W2(-1 + 3) 085011-012700

g-band : CCD#03 missing

W2(+1 + 1) 085749-031900 y-band observations

W2(+3 + 1) 090526-031900

g-band : CCD#03 missing

W2(+3 + 2) 090526-022300

g-band : CCD#03 missing

W2(+3 + 3) 090526-012700

g-band : CCD#03 missing

W2(+2 + 2) 090137-022300 y-band observations

W3(-3 + 1) 135846+552631 y-band observations

W3(-2 -0) 140525+543031

u*,g,r,i,z contamination: Messier 101 galaxy on the 4th (bottom right) MegaCam quadrant

W3(-2 -1) 140540+533431 y-band observations

W3(-2 + 1) 140509+552631 y-band observations

W3(-2 + 3) 140433+571831 y-band observations

W3(-1 + 3) 141113+571831 y-band observations

y-band radial astrometric offset 0.077"

W3(-0 -1) 141754+533431

g-band seeing anomaly: 1.045"

W3(+3 -1) 143615+533431 y-band observations

W3(+3 + 2) 143728+562231 y-band observations

W4(+1 - 1) 221706+002300

W4(-1 -1) 220930+002300 y-band observations

W4(-1 + 1) 220930+021500 y-band observations

W4(-1 + 2) 220930+031100 y-band observations

W4(-1 + 3) 220930+040700 y-band observations

W4(-2 + 2) 220542+031100 y-band observations

W4(-2 + 3) 220542+040700 y-band observations

W4(-3 + 3) 220154+040700 y-band observations







Table 15: CFHTLS Wide stacks with exceptions or anomalies (cont’d).