de Vaucouleurs Model Parameters - Stack Photometry versus Full Force Photometery

Back in February we presented the first results of the new IPP programs psphotFullForce ​http://svn.pan-starrs.ifa.hawaii.edu/trac/ipp/wiki/fullforce_SAStest1.

There we presented plots that send to indicate that the full force results provided a much better match to SDSS model fits than the psphotStack results for de Vaucouleurs models (dev) There was some scepticism that the difference was so great. In particular the validity of the ​plot was doubted.

It turns out that this scepticism was justified. The ddevrad values for the stack photometry were incorrect (the difference in units between the sdss value (arcseconds) and the IPP values (pixels) was not accounted for. Upon further review we discovered that the wrong stacks (label SAS.20130620) were used for that investigation rather than the SAS 32 stacks (label SAS.20130703).

In order to examine the results in more detail we re-ran the full force pipeline on a subset of the SAS skycells, selecting only deV models for forced photometry. Recall that by default the "best" of the three models fit during stack photometry is used. The skycells chosen were near the center of the SAS field: 332 < ra < 336, -3 < dec < 3.