[KIDS] comparison of KIDS to SDSS photometry

[Francesco La Barbera]

Dear Gijs,

thank you very much for the effort to put this material on the wiki.
I wilI look into this and  discuss it with Mario on Monday morning too.

[]s,
Francesco

On Fri, Nov 30, 2012 at 12:51 AM, Gijs Verdoes Kleijn
<verdoes at astro.rug.nl>wrote:

>  Dear Francesco and Mario,
>
> FYI,
> While digesting the valuable information in your plots I already put some
> of the material on the wiki in the KiDS-INT-DR2 cookbook area:
>
> http://wiki.astro-wise.org/projects:kids:data_deliveries:internaldelivery2.0_cookbook#kids_vs_sdss
> Hope this helps you as well and please have a look to improve my wording
> if you find the time.
>
> Best wishes, Gijs
>
> Op 28-11-2012 10:21, Francesco La Barbera schreef:
>
> Dear All,
>
>  I  summarize  here  the  comparison  of KIDS  to  SDSS  photometry  we
> (Mario+me) have performed so far for  the 52 coadds of KIDS INTR2. All
> plots are included in the attached archive.
>
>  Mario has  also performed a  comparison to CFHTLS  as well as  a first
> attempt to characterize of color terms using SDSS and CFHTLS data, but
> I'm not going to include it in  here (we didn't have much time to look
> at it in detail, so far).
>
>  We have matched the KIDSCAT catalogs to SDSS DR8, separating stars and
> galaxies according to SDSS classification.
>
>  The plots
>
>  sdss_${SOURCE}_${BAND}_${FIELD}_full_DR8.png
>
>  show differences  in magnitude as a  function of RA  (upper panel) and
> DEC (lower panel), where
> SOURCES -> gal/st refer to galaxies and stars, respectively
> BAND -> ugri
> FIELD -> f135 plots the three fields with RA~131, 135, and 139
>          f185 plots the ten fields with RA~184, 185, and 186
>
>  We  are using  petromags  from  SDSS (for  both  stars and  galaxies).
> KIDSCAT  mags have  been  interpotaled to  match  the SDSS  4xPetroRad
> (diameter) aperture  for each object.   Lines are running  medians for
> different bands/pointings (the u-band comparison for galaxies is quite
> meaningless,  considering the  low S/N  of SDSS  u-band  data). Median
> KIDS-SDSS offsets have been subtracted off for each field.
>
>  On  average, the  agreement is  good, with  no  significant variations
> (larger than a few cenths of  mags) across the fields. This is further
> shown in the attached plots
>
>  cmp_${BAND}band_phot_ra_dec_${SOURCES}_errmag0.05.jpg
>
>  where
>
>  BAND->ugri
> SOURCES-> stars/galaxies
>
>  plotting magntiude  differences as a function  of RA and  DEC with all
> fields overplotted (after subtracting off the RA and DEC of each coadd
> center).   Median magnitude  offsets have  been removed  (as  done for
> previous  plots),  and  only   objects  with  better  SDSS  photometry
> (petroerr_mag<0.05mag) have been  selected. Circles plot all available
> sources (for  all 13  coadds in each  band). Curves  are median-binned
> trends (each bin including the same number of objects), with different
> colors corresponding to different  fields. Notice that the u-band plot
> for galaxies is not included, for the reasons mentioned above.
>
>  Finally, the plots
>
>  off_${BAND}band_phot_ra_dec_${SOURCES}_errmag0.05.jpg
>
>  show  the distribution  of median  magnitude  offsets for  all the  13
> fields available in  each band.  In general, the  distributions have a
> width  of a  few cenths  of mags,  but in  one  case (KIDS_185.0_-0.5,
> g-band) there is a large offset of ~0.1mag. We think it's important to
> investigate why this happened.
>
>  I'm also  attaching two tables  (produced by Mario, hopefully  in wiki
> format)  summarizing the  the median  offsets, mad,  and peak  to peak
> amplitudes  in RA  and DEC  (to have  an upper  value to  the internal
> photometric accuracy):
>
>  ov_sdss_gals.tab
> ov_sdss_stars.tab
>
>  If  necessary, I can  provide further  details/info on  the comparison
> during today's teleconf. We'll try to put all this material on the wiki as
> soon as possible.
>
>  Cheers,
> Francesco & Mario
>
>
>
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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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