Quasars with redshifts greater than 4 are rare, and can be used to probe the
structure and evolution of the early universe. Here we report the discovery of
six new quasars with i-band magnitudes brighter than 19.5 and redshifts
between 2.4 and 4.6 from the YFOSC spectroscopy of the Lijiang 2.4m telescope
in February, 2012. These quasars are in the list of z>3.6 quasar candidates
selected by using our proposed J−K/i−Y criterion and the photometric redshift
estimations from the SDSS optical and UKIDSS near-IR photometric data. Nine
candidates were observed by YFOSC, and five among six new quasars were
identified as z>3.6 quasars. One of the other three objects was identified as
a star and the other two were unidentified due to the lower signal-to-noise
ratio of their spectra. This is the first time that z>4 quasars have been
discovered using a telescope in China. Thanks to the Chinese Telescope Access
Program (TAP), the redshift of 4.6 for one of these quasars was confirmed by
the Multiple Mirror Telescope (MMT) Red Channel spectroscopy. The continuum and
emission line properties of these six quasars, as well as their central black
hole masses and Eddington ratios, were obtained.Comment: 7 pages, 2 figures, published in Research in Astronomy and
Astrophysics (RAA) as a lette
