Image Details
Caption: Figure 9.
Forced photometry using The Tractor, contrasted with traditional “catalog-matching.” Left: color–color diagram of catalog-matched PSF sources from the Legacy Surveys and AllWISE catalogs. Right: color–color diagram of PSF sources from the Legacy Survey catalogs that have no matching object in the AllWISE catalog. Many of these will be sources that are well detected in the Legacy Surveys optical imaging, but below the detection threshold in the WISE imaging. We have applied a cut to show only WISE flux measurements above 3σ; with this cut, we nearly double the number of sources with measured WISE fluxes. The distributions shown in both panels are similar, demonstrating that the forced photometry measurements of the faint mid-infrared sources make astrophysical sense, despite being noisier.
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