Star / Galaxy / CR Separation in PS1

-- Eddie Schlafly & Eugene Magnier

We have used GPC1 observations of Stripe 82 to define the PS1 Star / Galaxy / CR separation. The advantage of this region is that SDSS data exists for both single pass and deep stack analysis.

We looked at several parameters measured by the IPP psphot tool which may be sensitive to the difference between stars and galaxies. We used the SDSS star/galaxy separation from both the single pass and the deep stack images as 'truth'. Our main conclusion is that a simple comparison between the PSF and Kron magnitudes for objects does a good job of reproducing the SDSS star/galaxy separation for signal-to-noise > 10.0 For signal-to-noise between ~6.5 and 10.0, the two populations start to blurred together significantly. For S/N < 6.5, we are unable to distinguish stars and galaxies.

We found that the moments did not improve the star/galaxy separation. Instead, because of the variable PSF, including moment information tended to increase the noise in the measurement.