DES-SDSS Color Terms¶
SV requirements and goals associated with this analysis¶
- Synthetic SDSS ugriz, UKIDSS Yab, and DES grizY magnitudes were
generated by Sahar Allam using the Pickles (1998) stellar library
and David James' and Huan Lin's DES filter response curves from
- Real DECam data were taken from the NCSA DESDM standard star processing for
the night of November 3 (griz). (For Y-band, the data were taken from
Huan Lin's coadd of the November 2 and 4 starflat.)
- Plots of "mag_DES - mag_SDSS" vs. SDSS color were generated for both sets
of data and compared:
- Results of fit of the above plots to a straight line
(the color term coefficient "b" is then the slope of
the straight line):
|filter||range of fit||b_synth||b_observed||b_synth - b_observed||Comments for Cal-R2/Cal-R3|
|g||0 < g-r < 1||-0.084||-0.103||+0.019||w/in spec|
|r||0 < g-r < 1||-0.087||-0.080||-0.007||w/in spec|
|i||0 < i-z < 1||-0.324||-0.298||-0.026||marginally out of spec|
|z||0 < i-z < 1||-0.080||-0.086||+0.006||w/in spec|
|Y||-0.3 < z-Y < 0.3||+0.409||+0.261||+0.148||out of spec|
Results (as of Nov 24, 2012)¶
- The Cal-R2 requirement has been met.
- g w/in spec
- r w/in spec
- i marginally out-of-spec
- z w/in spec
- The Cal-R3 requirement has not been met.
- Y out of spec
- The observed color term is shallower than expected.
- It does, however, have the right sign and generally the right shape.
- That said, I would not delay DES operations on account of failing to meet this particular requirement.
- The Cal-G7 goal has not yet been met.
- g not in spec
- r not in spec
- i not in spec
- z not in spec
- Y not in spec
- The Cal-G8 goal is TBC.