Discovery of eight z ~ 6 quasars from Pan-STARRS1
  High-redshift quasars are currently the only probes of the growth of
supermassive black holes and potential tracers of structure evolution at early
cosmic time. Here we present our candidate selection criteria from the
Panoramic Survey Telescope & Rapid Response System 1 and follow-up strategy to
discover quasars in the redshift range 5.7<z<6.2. With this strategy we
discovered eight new 5.7<z<6.0 quasars, increasing the number of known quasars
at z>5.7 by more than 10%. We additionally recovered 18 previously known
quasars. The eight quasars presented here span a large range of luminosities
(-27.3 < M_{1450} < -25.4; 19.6 < z_ps1 < 21.2) and are remarkably
heterogeneous in their spectral features: half of them show bright emission
lines whereas the other half show a weak or no Ly$\alpha$ emission line (25%
with rest-frame equivalent width of the Ly$\alpha$ + Nv line lower than
15{\AA}). We find a larger fraction of weak-line emission quasars than in lower
redshift studies. This may imply that the weak-line quasar population at the
highest redshifts could be more abundant than previously thought. However,
larger samples of quasars are needed to increase the statistical significance
of this finding.
