[KIDS] completeness/contamination

[Francesco La Barbera]

Dear All,

we performed a more detailed study of completeness/contamination of our
KIDS catalogs by comparing
KIDS vs. CFHT photometry in the field of KIDS_135_-1.5.

Here it's the steps we followed:

1) We downloaded the last version of the images, that   shouldn't be
affected
by the satellite track issue we found in the previous version of the
coadd's.

1) We ran KIDSCAT on the r-band images, with 6 different setups, changing
DETECTION_MINAREA
and DETECTION_THRESHOLD in the S-Ex .configuration file. We considered:
MINAREA: 3, 5
THRESHOLD: 1.5, 2.0, 2.5
Besides that, we also ran KIDSCAT on the g and i band images with
MINAREA=3, and THRESHOLD=2.0, 2.5


2) The catalogs were matched to the CFHT ones (pls ask Mario for details)

3) The first attached plot, CFHT_KIDS_....._THRESHOLD.jpg, summarizes the
completeness/contamination with different setups for the r-band coadd.
Top and bottom panels correspond to MINAREA=3 and 5, respectively.
For each panel, the solid curves plot the fraction of spurious sources
(i.e. objects with no matching to CFHT)
as a function of magnitude. We considered magnitudes in the same aperture
of 5'' in both catalogs (KIDS and CFHT).
Curves with different colors correspond to different DETECTION_THRESHOLDs
as labeled.
The completeness mags, for each THRESHOLD value (i.e. color), are marked
with a vertical dashed line.
(Here completeness is defined as the mag value where CFHT counts keep
increasing, while KIDS counts remain constant/decrease).

4) The second attached plot shows the spatial distribution of spurious
sources in the area "previously" affected by the satellite track.

5) We would conclude as follows:
 A) for THRESHOLD=1.5 contamination increases significantly, up to ~20-22%
around the completeness mag
 B) completeness improves by ~0.15-0.2mag when moving from THRESHOLD 2.5 to
2.0, and by the same amount from 2.0 to 1.5.
 C) changing MINAREA to 5 we get slightly lower completeness
(by~0.1-0.15mag), and slightly lower contamination (by a few percent)
 D) the satellite track issue is still there

Depending on what is the maximum level of contamination we can allow in the
catalogs, we think we might adopt either THRESHOLD=2.5 (current value)
or THRESHOLD=2.0, as in the latter value we get slightly better
completeness, at the price of a bit worst contamination.
Notice that the contamination fractions are indeed upper limits (see our
previous email on the subject), as there are many sources
not present in the CFHT catalogs  because of (e.g.) deblending issues.

Finally, the last attached plot,
  CFHT_KIDS_COMPLETENESS_CONTAMINATION_THRESHOLD_g_i_bands.jpg, shows
completeness and contamination
for g band (upper panel) and i band (lower panel), both for MINAREA=3.
Resuts are similar to those for r band.

Eagerly waiting for your feedback, so that we can finalize the S-Ex
configuration file.

Cheers,
Francesco, Nicola, Mario

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