Machine learning photometric redshifts

Apart from the template-fitting photometric redshifts included in the DR3 catalog, photometric redshifts based on two separate machine-learning techniques (MLPQNA and ANNz2) are also provided.

MLPQNA photometric redshifts and PDFs

For the DR3 data set photometric redshifts have been derived using the Multi Layer Perceptron with Quasi Newton Algorithm (MLPQNA) technique, following the a similar strategy as was done for DR2 (Cavuoti et al. 2015, MNRAS, 452, 3100). Driven by the magnitude ranges covered by the spectroscopic knowledge base (SDSS DR9 and GAMA DR2), the total number of sources with MLPQNA photo-z's is 8,582,152. Photo-z probability distribution functions (PDFs) were also derived.

Catalog format

The best-guess photometric redshifts derived using the MLPQNA technique are provided in a single catalogue, featuring the columns listed in the following table. Apart from the photo-z values the only content consists of source ID information and positions that allow straightforward association with the KiDS DR3 multi-band catalogue.

LabelFormatUnitDescription
ID25ASource identifier
SLIDJAstro-WISE SourceList identifier
SIDJAstro-WISE Source identifier
RAJ2000DdegRight ascension
DECJ2000DdegDeclination
Z_MLPQNADBest MLPQNA predicted photometric redshift

 

Also available are photo-z Probability Distribution Functions (PDFs) based on the MLPQNA technique. These are provided in separate catalog files per DR3 survey tile, and their format is specified in the following table . Again, included data is limited to the PDF bins and source ID and position information that can be used to associate to the DR3 multi-band catalogue.

LabelFormatUnitDescription
ID25ASource identifier
SLIDJAstro-WISE SourceList identifier
SIDJAstro-WISE Source identifier
RAJ2000DdegRight ascension
DECJ2000DdegDeclination
PDF001DMLPQNA photo-z PDF bin 1 (z=0.01)
.........
PDF350DMLPQNA photo-z PDF bin 350 (z=3.5)

 

Catalog download

The catalog with the best photo-z estimates can be downloaded via the following link.

The PDFs are distributed in a separate FITS catalog for each of the DR3 survey tiles; the total size of these catalogs is 23 GB. Downloading of these files is possible with wget using the input files linked below. The also provided md5sums file can be used to verify your downloaded files with the command "md5sum -c kids_dr3.2_mlpqnapdf_md5sums.txt".

ANNz2 photometric redshifts

Photometric redshifts have also been derived using the ANNz2 method (Sadeh et al. 2016, PASP, 128, 104502) and a knowledge base that includes spectra from several deep spectroscopic fields. The catalog contains all sources with good GAaP photometry in all four filters (39,166,070 sources). Also included is a "fiducial" flag that identifies the most reliable set, removing artefacts, stars and sources in parameter space poorly sampled by the knowledge base; these filters result in a set of approximately 19.2 million reliable photo-z's.

Catalog format

The best-guess photometric redshifts derived using ANNz2 are provided in a single catalogue, featuring the columns listed in the following table. Apart from the photo-z values, source ID information and positions that allow straightforward association with the KiDS DR3 multi-band catalogue, and the fiducial flag that identifies the most reliable values are provided.

LabelFormatUnitDescription
ID25ASource identifier
RAJ2000DdegRight ascension
DECJ2000DdegDeclination
zphot_ANNz2DBest ANNz2 predicted photometric redshift
fiducialIFlag defining fiducial selection

 

Catalog download

The catalog with the best photo-z estimates can be downloaded via the following link.