Identification of BASS DR3 Sources as Stars, Galaxies and Quasars by
  XGBoost
  The Beijing-Arizona Sky Survey (BASS) Data Release 3 (DR3) catalogue was
released in 2019, which contains the data from all BASS and the Mosaic z-band
Legacy Survey (MzLS) observations during 2015 January and 2019 March, about 200
million sources. We cross-match BASS DR3 with spectral databases from the Sloan
Digital Sky Survey (SDSS) and the Large Sky Area Multi-object Fiber
Spectroscopic Telescope (LAMOST) to obtain the spectroscopic classes of known
samples. Then, the samples are cross-matched with ALLWISE database. Based on
optical and infrared information of the samples, we use the XGBoost algorithm
to construct different classifiers, including binary classification and
multiclass classification. The accuracy of these classifiers with the best
input pattern is larger than 90.0 per cent. Finally, all selected sources in
the BASS DR3 catalogue are classified by these classifiers. The classification
label and probabilities for individual sources are assigned by different
classifiers. When the predicted results by binary classification are the same
as multiclass classification with optical and infrared information, the number
of star, galaxy and quasar candidates is separately 12 375 838 (P_S>0.95), 18
606 073 (P_G>0.95) and 798 928 (P_Q>0.95). For these sources without infrared
information, the predicted results can be as a reference. Those candidates may
be taken as input catalogue of LAMOST, DESI or other projects for follow up
observation. The classified result will be of great help and reference for
future research of the BASS DR3 sources.
