[KIDS] KIDSCAT mag lim implementation
Gijs Verdoes Kleijn
verdoes at astro.rug.nl
Thu Nov 22 12:07:54 CET 2012
Dear Jelte et al.,
FYI,
Francesco and I have been maintaining lim. mag. results at
http://wiki.astro-wise.org/projects:kids:data_deliveries:internaldelivery2.0#catalog_extraction
which includes comparison to predictions and idea of sensitivity decreases.
Cheers, Gijs
On 11/22/2012 12:00 PM, Jelte de Jong wrote:
> Dear Francesco,
>
> the limiting mags, as written in the original proposal, are the following:
> u: 24.8
> g: 25.4
> r: 25.2
> i: 24.2
> (see also for example on the KiDS website:
> http://kids.strw.leidenuniv.nl/techspecs.php).
>
> Seems to me that we're off by about 0.4 mag, of which 0.3 is probably
> attributable to the decrease of throughput of the system due to mirror
> reflectivity?
> Btw, we should be able to see this by looking at the limiting mags as
> function of observation date. Would be interesting to verify this.
>
> Cheers,
> Jelte
>
> On 22/11/12 09:53, Francesco La Barbera wrote:
>> Dear Gijs, et al.,
>>
>> On Thu, Nov 22, 2012 at 6:44 AM, Gijs Verdoes Kleijn
>> <verdoes at astro.rug.nl <mailto: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
>> <mailto:e-mail%3Averdoes at astro.rug.nl> | OmegaCEN / Kapteyn
>> Institute / |
>> |www:www.astro.rug.nl/~verdoes
>> <http://www.astro.rug.nl/%7Everdoes> | Target
>> |
>> |tel: +31-50-3638326 <tel:%2B31-50-3638326> |
>> University of Groningen |
>> |mobile: +31-654658050 <tel:%2B31-654658050> | postal
>> address: |
>> | | Kapteyn Astronomical Institute |
>> | | Postbus 800, 9700 AV, Groningen|
>> | | The Netherlands |
>> --------------------------------------------------------------------
>>
>>
>>
>>
>> _______________________________________________
>> KiDS mailing list
>> KiDS at astro-wise.org
>> http://listman.astro-wise.org/mailman/listinfo/kids
>
> --
> Dr. Jelte T. A. de Jong
> Sterrewacht Leiden
> Leiden University, Leiden, the Netherlands
> E:jelte at strw.leidenuniv.nl
> T: +31-(0)715275818
> W: jelte.jdejong.net
>
>
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--
--------------------------------------------------------------------
|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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