Quasar catalog

A catalog of quasars selected from KiDS DR3 is provided. The quasars are identified by the Random Forest supervised machine learning model, trained on SDSS DR14 spectroscopic data. The identification is performed on a pre-prepared KiDS inference set, cleaned up of excessively noisy, missing or otherwise problematic measurements, and additionally trimmed at r<22 to avoid extrapolation beyond the coverage of the training set. This gives 3.4 million objects in the final inference sample, from which the Random Forest identified 190,000 quasar candidates. Please see Nakoneczny et al. (submitted) for details. Please cite that paper together with the main KiDS DR3 one (de Jong et al. 2017, A&A, 604, A134, arXiv:1703.02991) if you use the data described here.

The released catalog includes all the KiDS DR3 objects which were subject to the classification (the inference set). Apart from basic columns taken from KiDS DR3 (IDs and coordinates), we add the resulting probabilities for each class in QSO, STAR and GALAXY columns. The final classification, given by the class with the highest probability, is provided in the CLASS column. To obtain the full catalog of all the 190k quasars candidates, one has to query CLASS == "QSO", while the high purity catalog is accessible by taking QSO > 0.8 (see Nakoneczny et al. subm. for more details of various quality cuts).

Catalog download

The link to the catalog is provided below.


Users of these data should cite Nakoneczny et al. (submitted) and the DR3 release paper (de Jong et al. 2017, A&A, 604, A134, arXiv:1703.02991) and include the KiDS DR3 acknowledgements.

Catalog description

The table below provides brief descriptions for the catalog columns. We refer to Nakoneczny et al. (2018, subm.) for details on how the catalog was obtained and a more detailed description of its content and characteristics.

ID stringQuasar name (KDR2_JHHMMSS.s+DDMMSS)
RAJ2000 floatdegRight Ascension in decimal degrees (J2000)
DECJ2000floatdegDeclination in decimal degrees (J2000)
CLASS stringSource classification
GALAXY floatProbability of being a galaxy
QSO floatProbability of being a QSO
STAR floatProbability of being a star