Abstract
We present the discovery and spectroscopic confirmation with the ESO NTT and
Gemini South telescopes of eight new 6.0 < z < 6.5 quasars with z$_AB$ <
21.0. These quasars were photometrically selected without any star-galaxy
morphological criteria from 1533 deg$^2$ using SED model fitting to
photometric data from the Dark Energy Survey (g, r, i, z, Y), the VISTA
Hemisphere Survey (J, H, K) and the Wide-Field Infrared Survey Explorer (W1,
W2). The photometric data was fitted with a grid of quasar model SEDs with
redshift dependent Lyman-\alpha forest absorption and a range of intrinsic
reddening as well as a series of low mass cool star models. Candidates were
ranked using on a SED-model based $\chi^2$-statistic, which is extendable to
other future imaging surveys (e.g. LSST, Euclid). Our spectral confirmation
success rate is 100% without the need for follow-up photometric observations as
used in other studies of this type. Combined with automatic removal of the main
types of non-astrophysical contaminants the method allows large data sets to be
processed without human intervention and without being over run by spurious
false candidates. We also present a robust parametric redshift estimating
technique that gives comparable accuracy to MgII and CO based redshift
estimators. We find two z $\sim$ 6.2 quasars with HII near zone sizes < 3
proper Mpc which could indicate that these quasars may be young with ages <
10$^6$ - 10$^7$ years or lie in over dense regions of the IGM. The z = 6.5
quasar VDESJ0224-4711 has J$_AB$ = 19.75 is the second most luminous quasar
known with z > 6.5.
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