[KIDS] KIDSCAT mag lim implementation

[Francesco La Barbera]

Dear Gijs, et al.,

On Thu, Nov 22, 2012 at 6:44 AM, Gijs Verdoes Kleijn
<verdoes at astro.rug.nl>wrote:

> Dear Francesco et al,
>
> Many thanks for the input Francesco. I bring this conversation now into
> the mailinglist space to ease following the discussion.
>
>
OK!


> I ran the procedure for all 52 fields. The procedure produces a single
>> plot, with SNR as a function
>> of 2'' diameter mag. One example is attached here, for the field
>> KIDS_185.0_1.5.r.
>> Black points are all good (flag==0) objects in the field. In red you can
>> see the median trend, while
>> the blue curve is the analytic fit
>> p_1*flux/(p_2*flux+p_3)
>> where p_1, p_2, and p_3 are free fitting parameters.
>>
> Looks good! Could you share the script you are using? Then Hugo and I will
> make a python version of it as part of the QC script for sourcelists.
>
>
I'm attaching here the fortran program, which is part of KIDSCAT now. In
order to compile it, you
need the port library+pgplot. Binary versions of these libraries were
already included in the first KIDSCAT internal release. You should have
them already, otherwise, pls, just lemme know.


> The series of 4 (5?) curves are due to discrete steps in integration times
> due to the dither pattern, right?
> The displacement in magnitude seem in rough agreement with that idea:
> >>> -2.5*math.log10(4/5.)
> 0.24227503252014099
> >>> -2.5*math.log10(3/5.)
> 0.55462187404089092
> >>> -2.5*math.log10(1/5.)
> 1.7474250108400469
> >>> -2.5*math.log10(2/5.)
> 0.99485002168009395
>
>
> Yup, different patterns correspond to objects in regions with different
texp (because of dithering).
Your figures further confirm this.

>
>> The analytic fit is used to compute the typical mag corresponding to
>> SNR_LIMIT=5 (see dashed and
>> solid black lines in the plot). This is our limiting mag.
>> The procedure also computes the same kind of limit but for different
>> SNR_LIMIT(i.e. 10 and 15). These
>> values are stored in an ascii file (MLIM.dat), into the subdirectory
>> OUTPUT_RES.
>>
> Good. Please store the analytic fit parameters as well. Those will come in
> handy.
>
> Done. In the ascii file MLIM.dat, we also have now a third column with p_i.


>
>> I made some tests according to what we mentioned some time ago:
>> 1) I can confirm that computing SNR from either FLUXERR or MAGERR doesn't
>> make any difference at all (just a sanity check);
>>
> Good.
>
>  2) using different detection tresholds does not change significantly the
>> mag lim estimates; the second attached plot
>> shows the effect of decreasing DETECT_TRESH from 2.5 to 2.0 for the same
>> fit as in the example. The mag lim goes
>> from 24.77 to 24.78!!
>>
> Good to know MAG_APER at 2" diameter is very insensitive to this change in
> DETECT_THRESH. That might be different for e..g, MAG_ISO. For now I think
> it is enough to restrict the lim. mag. analysis to MAG_APER with 2". For
> those we have predictions we can compare to (in KiDS proposal). KiDS team
> meeting is a good opportunity if/how we need to extend the lim. mag.
> analysis.
>

Could you kindly provide us the predictions (the ones in hte porposal) for
different wavebands ? We (Nicola+me) are performing a systematic comparison
to predicted mag_lim's, and want to be sure to use correct values.

Of course, the meeting will be an excellenet opportunity to discuss
possible extensions....

Cheers!
F.

Best wishes, Gijs
>
>
>> Pls, lemme know whatever comment/suggestion you have. Also, do we
>> want/need compute other limiting mags
>> (e.g. using MAGAUTO/different apertures)???
>>
>> Cheers,
>> Francesco
>>
>>
> --
> ------------------------------**------------------------------**--------
> |dr Gijs Verdoes Kleijn         |   astronomer                     |
> |e-mail:verdoes at astro.rug.nl    |   OmegaCEN / Kapteyn Institute / |
> |www:www.astro.rug.nl/~verdoes  |   Target                         |
> |tel: +31-50-3638326            |   University of Groningen        |
> |mobile: +31-654658050          |   postal address:                |
> |                               |   Kapteyn Astronomical Institute |
> |                               |   Postbus 800, 9700 AV, Groningen|
> |                               |   The Netherlands                |
> ------------------------------**------------------------------**--------
>
>
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