http://arxiv.org/abs/1706.09507
In this paper we present and characterize a nearest-neighbors color-matching photometric redshift estimator that features a direct relationship between the precision and accuracy of the input magnitudes and the output photometric redshifts. This aspect makes our estimator an ideal tool for evaluating the impact of changes to LSST survey parameters that affect the measurement errors of the photometry, which is the main motivation of our work (i.e., it is not intended to provide the “best” photometric redshifts for LSST data). We show how the photometric redshifts will improve with time over the 10-year LSST survey and confirm that the nominal distribution of visits per filter provides the most accurate photo-$z$ results. We also demonstrate how deep LSST imaging of a spectroscopic galaxy sample can significantly improve photo-$z$ quality, especially in the survey’s early years. The LSST survey strategy naturally produces observations over a range of airmass, which offers the opportunity of using an SED- and $z$-dependent atmospheric affect on the observed photometry as a color-independent redshift indicator. We show that measuring this airmass effect and including it as a prior has the potential to improve the photometric redshifts and can ameliorate extreme outliers, but also find that it will only be adequately measured for the brightest galaxies, which limits its overall impact on LSST photometric redshifts. Ultimately, we intend for this work to serve as a guide for the expectations and preparations of the LSST science community with regards to the minimum quality of photo-$z$ as the survey progresses.
M. Graham, A. Connolly, Z. Ivezic, et. al.
Fri, 30 Jun 17
26/65
Comments: 25 pages, 16 figures, 2 tables, submitted to AJ