KiDS1000 catalogue: Redshift distributions and their calibration
Abstract
We present redshift distribution estimates of galaxies selected from the fourth data release of the KiloDegree Survey over an area of ∼1000 deg^{2} (KiDS1000). These redshift distributions represent one of the crucial ingredients for weak gravitational lensing measurements with the KiDS1000 data. The primary estimate is based on deep spectroscopic reference catalogues that are reweighted with the help of a selforganising map (SOM) to closely resemble the KiDS1000 sources, split into five tomographic redshift bins in the photometric redshift range 0.1 < z_{B} ≤ 1.2. Sources are selected such that they only occupy that volume of ninedimensional magnitudespace that is also covered by the reference samples (`gold' selection). Residual biases in the mean redshifts determined from this calibration are estimated from mock catalogues to be ≲0.01 for all five bins with uncertainties of ∼0.01. This primary SOM estimate of the KiDS1000 redshift distributions is complemented with an independent clustering redshift approach. After validation of the clusteringz on the same mock catalogues and a careful assessment of systematic errors, we find no significant bias of the SOM redshift distributions with respect to the clusteringz measurements. The SOM redshift distributions recalibrated by the clusteringz represent an alternative calibration of the redshift distributions with only slightly larger uncertainties in the mean redshifts of ∼0.01 − 0.02 to be used in KiDS1000 cosmological weak lensing analyses. As this includes the SOM uncertainty, clusteringz are shown to be fully competitive on KiDS1000 data.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 March 2021
 DOI:
 10.1051/00046361/202039018
 arXiv:
 arXiv:2007.15635
 Bibcode:
 2021A&A...647A.124H
 Keywords:

 cosmology: observations;
 gravitational lensing: weak;
 galaxies: photometry;
 surveys;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Instrumentation and Methods for Astrophysics
 EPrint:
 15 pages, 7 figures, 3 tables, accepted for publication in A&