Star/Galaxy Separation (PDR2)

The {filter}_extendedness_value parameter, which is based on the difference between the CModel and PSF magnitudes (dmag=0.015 is the threshold), is a reasonable star/galaxy classifier.  Using the star/galaxy separation from HST/ACS in COSMOS as the truth table, here we characterize the accuracy of our star/galaxy separation.  The completeness is defined as a fraction of ACS stars properly classified as stars in HSC. The contamination is a fraction of ACS galaxies among objects classified as stars in HSC.  Both the completeness and contamination rates are strong function of the seeing size and depth.  Note that the extendedness parameter is a simple parameter and those who are interested in more accurate star/galaxy classification are encouraged to explore various cuts on |cmodel_mag – psf_mag|.

0.5 arcsec at Wide-depth
0.7 arcsec at Wide-depth
1.0 arcsec at Wide-depth
0.7 arcsec at UltraDeep-depth