Known Problems in Photo v5_2

The following problems are known to be present in the v5_2 data used in the EDR, and have been fixed in the latest version of photo:
PR 2244 Blended objects with NCHILD=0 do not have NODEBLEND set. Fixed in v5_2_18.
PR 1214 Deblending children flux assignments changed drastically since 5_0_3
The Deblender shreds some bright galaxies inconsistently in different bands, producing a collection of `galaxies' with weird colours. Details
PR 1355 velocity errors are being underestimated for known quasars
PR 1496 Very faint object has petroMag ~ 13.5
PR 1521 petroCounts error wrong if NOPETRO
PR 2013 Bright galaxy's Petrosian and model magnitudes can differ by up to 1.5mags
PR 2190 bright star centroids are bad (at the level of < 100 mas)
PR 2155 petroRadErr can be negative
PR 2171 astrom_floor is only added in quadrature to {rowc,colc}Err for some objects
PR 1944 Likelihoods typically underflow for very bright objects
PR 974 Model colors for objects not detected in r' not being done consistently
PR 613 ab_deV and/or ab_exp can be negative
A consequence of this is that the model flux can be negative.
PR 598 There are no photo errors for petroR50 and petroR90
PR 69 Model-fitting of bright stars should return high PSF likelihood
PR 161 CR's are not always cleaned completely
PR 164 Saturation trails appear as ghosts on other half of the CCD
PR 640 Model colors of stars have testbed problems absent in photo 5.0.3

Details of Resolved Problems

Details on PR 1214

Such problems are best illustrated in an g'-r'-i' colour composite of the parent (in the top left corner). In both cases the images are stretched from 0 : 150 sigma using a sqrt map; this brings out faint features which have essentially no impact on the photometry.

A Bad Deblend


The v5_2_14 deblend of an r' ~ 11.3 galaxy with an r' ~ 13 (slightly saturated) star. Note that the flux is allocated to different children in wildly inconsistent ways.

The v5_3 deblend of the same system. All children have `astrophysical' colours (the removal of a part of the lower-left corner of the galaxy into a separate child is a result of this galaxy touching the edge of the chip).

The principal child has:

                   u'           g'           r'           i'           z'
psfMag:            18.02        16.53        16.36        16.55        17.55 
psfColour:                1.49         0.17         -0.19        -1.00       
modelMag:          13.48        11.81        11.71        11.97        13.26 
petroMag:          13.78        11.95        11.88        12.20        13.65 

A more typical case

This is not the typical behaviour; for example, out of 26 Zwicky galaxies lying in the `testbed' area of runs 745/756, the only one that shows problems (in both v5_2 and v5_3) has a saturated r' ~ 11.9 star 5" from the centre of a spiral

One of the other Zwicky galaxies in this area of the sky is shown here:



                    u'           g'           r'           i'           z'
psfMag:             19.17        17.34        16.53        15.90        15.57 
modelMag:           17.01        15.40        14.61        14.06        13.60 
petroMag:           16.48        14.54        13.92        13.63        13.99