Coadd level catalogs include the flag ‘detect_isPrimary’, a flag used to cull catalogs of duplicate (tract/patch overlap), non-deblended parent sources (deblend_nChild > 0) and sky objects. As such, this flag allows for a quick extraction of a scientifically useful subset from any given catalog. Until recently, no equivalent flag had existed for single-frame visit level catalogs. Ticket DM-25782 adds this functionality, introducing the ‘detect_isPrimary’ flag into visit level catalogs.
Currently, for the flag ‘detect_isPrimary’ to be True for any given visit level source, the source must have no deblended children (deblend_nChild == 0) and not be a sky source (sky_source is False). As a reminder, a sky source is a pseudo source injected into the detection list after source detection has taken place, randomly placed such that its footprint does not overlap with any other detected source footprint.
The figure below shows a zoomed in postage stamp from Visit 1228 (HSC-I) CCD 42, asinh scaled and smoothed with a Gaussian of FWHM 3 pixels. All sources identified as primary using ‘detect_isPrimary == True’ are shown using a blue square marker. Additionally, a number of sky sources that fall in this particular field of view are represented by orange plus markers. As expected, none of the sky sources shown here are identified as primary sources.
