[KIDS] update on completeness/contamination

[Gijs Verdoes Kleijn]

 Dear Francesco,  

 Thanks for these promising results.  The small fraction of spurious
detections for DETECT_THRESH=2.5 is promising to test lower detection
thresholds.   

 I cannot see the bright satellite residual in the KiDS_131.0_-1.5
coadds ready for quality assessment for KiDS-ESO-DR1:   

 You can access those using the link posted at
http://wiki.astro-wise.org/projects:kids:data_deliveries:kids-eso-dr1:sourcelists#comparison_to_cfhtls-w2.
 

 Can you confirm?  

 If so, I propose we start using those frames for the CFHTLS-W2
comparison.  

 Best wishes, Gijs   
 On Thu, 31 Jan 2013 11:57:07 +0100, Francesco La Barbera  wrote:  
Dear All,  
   here it's some updates about completeness/contamination estimates
in the CFHT overlap area, based   on the matched catalog produced by 
Mario.   
   The first attached plot is an updated version of what we have sent
yesterday, but now we also plot the fraction   of spurious sources,
i.e. contamination, as a function (KIDSCAT)
MAG_AUTO in the bottom
panel   of the same figure.   The fraction of "candidate spurious" is
defined as the ratio   
#OBJECTS_NOT_MATCHED_WITH_CFHT/#OBJECTS_MATCHED   
   The difference between the black adn red curve (bottom panel) is
that for the red curve I selected only KIDSCAT detections   with
SEX_FLAG==0|SEXFLAG>=16, hence removing sources blended with other
objects.   As you can see most of "candidate spurious" sources at
bright mags (they are not spurious, indeed, see below)  have been  
deblended by S-Ex.   
   The second attached plot shows the spatial distribution of
spurious sources, black and red colors have the same meaning as   
above. There are clearly some spurious features (e.g. detections
along a residual satellite track),   but in most cases (pls, compare
black vs. red dots), the "candidate spurious" objects are actually
deblended sources.   
   The third attached plot shows the spatial distribution of
"candidate spurious" (black circles) in a region around a
bright star
  (pixel coordinates x~25000, y~10000). Most of the objects are true
sources!! and they are actually missing in the   CFHT catalog (maybe,
they were just masked out by the CFHT masks).   
   Another example is the last attached file, contamination_2.jpg,
where you can clearly see "true spurious" objects   along a residual
satellite track. Other "spurious" are just S-Ex blends.   
   To summarize:   1) completeness estimates within KIDSCAT seem to
work OK, at least for this field where we have an external
comparison;   2) for what concerns the objects present only in the
KIDS image (not in the CFHT one), i.e. the possible spurious, we have
the following cases:     A) most of them are *true* sources, close to
brighter companions, likely detected only in KIDS because of the
better seeing wrt CFHT;     B) some of these "true" sources are not
present  in the CFHT catalog as they were  probalby masked out, for
some reason, in CFHT;     C) finally, we have "true"
contaminants,
mostly associated to satellite tracks, still present in the KIDS
image.   3) as a result, the red curve in bottom panel of
Fig.~CFHT_KIDS_COMPLETENESS_CONTAMINATION_135_-1.5_r.jpg gives    an
**upper** estimate of contamination in this r-band image.
Contamination is 
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