Ext. Sources with Extreme Colors & Integrated Fluxes

Blue Extended Src Candidates

For low source density fields, extended source candidates with extreme blue J-K colors, <0, are almost **always** artifacts: pieces of bright stars (halos, spikes, ghosts, persistence, etc). In turn, the bright star is usually located on a coadd edge.

Notes on blue outliers from low source density fields

Bottom line: apply color cut to eliminate these false extended sources.
J-K > 0, eliminates the worst offenders

Notes on red J-K outliers from low source density fields

Bottom line: most extreme red sources, J-K > 2, are either artifacts (pieces of bright stars) or they are real galaxies but affected by nearby bright stars (usually screwing up their J flux). Users must be careful with extended sources showing extreme colors, be it blue or be it red.

Bright stars (and their artifacts) on the edges of coadds much be carefully cleaned from the catalogs !!