A tiny fraction of the quasar population shows remarkably weak emission lines. Several hypotheses have been developed, but the weak line quasar (WLQ) phenomenon still remains puzzling. The aim of this study was to create a sizeable sample of WLQs and WLQ-like objects and to evaluate various properties of this sample. We performed a search for WLQs in the spectroscopic data from the Sloan Digital Sky Survey Data Release 7 based on Kohonen self-organising maps for nearly 10^5^ quasar spectra. The final sample consists of 365 quasars in the redshift range z=0.6-4.2 (z{bar}=1.50+/-0.45) and includes in particular a subsample of 46 WLQs with equivalent widths W_MgII_<11{AA} and W_CIV_<4.8{AA} We compared the luminosities, black hole masses, Eddington ratios, accretion rates, variability, spectral slopes, and radio properties of the WLQs with those of control samples of ordinary quasars. Particular attention was paid to selection effects.

Cone search capability for table J/A+A/568/A114/wlq (SDSS quasars with weak emission lines)