2016/12/31 by Le Zhang, Yu Yu, Pengjie Zhang
Physics and Astronomy · #Astronomy and Astrophysical Research #Cosmology #Factorization #Galaxies: Formation, Evolution, Phenomena #Matrix (chemical analysis) #Matrix decomposition #Outlier #Redshift #Stellar, planetary, and galactic studies #Weak gravitational lensing #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aa8c72
12 pages, 6 figures. Accepted for publication in ApJ. Updated to match the published version
openalex created_date 2017/01/06 · openalex publication_date 2017/10/10 · arxiv created 2017/10/12 · arxiv updated 2017/10/18 · openalex updated_date 2026/08/06
Abstract Photo- z error is one of the major sources of systematics degrading the accuracy of weak-lensing cosmological inferences. Zhang et al. proposed a self-calibration method combining galaxy–galaxy correlations and galaxy–shear correlations between different photo- z bins. Fisher matrix analysis shows that it can determine the rate of photo- z outliers at a level of 0.01%–1% merely using photometric data and do not rely on any prior knowledge. In this paper, we develop a new algorithm to implement this method by solving a constrained nonlinear optimization problem arising in the self-calibration process. Based on the techniques of fixed-point iteration and non-negative matrix factorization, the proposed algorithm can efficiently and robustly reconstruct the scattering probabilities between the true- z and photo- z bins. The algorithm has been tested extensively by applying it to mock data from simulated stage IV weak-lensing projects. We find that the algorithm provides a successful recovery of the scatter rates at the level of 0.01%–1%, and the true mean redshifts of photo- z bins at the level of 0.001, which may satisfy the requirements in future lensing surveys.