Three new VHS-DES Quasars at 6.7 < z < 6.9 and Emission Line Properties
  at z > 6.5
  We report the results from a search for z > 6.5 quasars using the Dark Energy
Survey (DES) Year 3 dataset combined with the VISTA Hemisphere Survey (VHS) and
WISE All-Sky Survey. Our photometric selection method is shown to be highly
efficient in identifying clean samples of high-redshift quasars leading to
spectroscopic confirmation of three new quasars - VDESJ 0244-5008 (z=6.724),
VDESJ 0020-3653 (z=6.834) and VDESJ 0246-5219 (z=6.90) - which were selected as
the highest priority candidates in the survey data without any need for
additional follow-up observations. The new quasars span the full range in
luminosity covered by other z>6.5 quasar samples (J AB = 20.2 to 21.3; M1450 =
-25.6 to -26.6). We have obtained spectroscopic observations in the near
infrared for VDESJ 0244-5008 and VDESJ 0020-3653 as well as our previously
identified quasar, VDESJ 0224-4711 at z=6.50 from Reed et al. (2017). We use
the near infrared spectra to derive virial black-hole masses from the
full-width-half-maximum of the MgII line. These black-hole masses are ~ 1 - 2 x
10$^9$M$_\odot$. Combining with the bolometric luminosities of these quasars of
L$_{\rm{bol}}\simeq$ 1 - 3 x 10$^{47}$implies that the Eddington ratios are
high - $\simeq$0.6-1.1. We consider the C\textrm{\textsc{IV}} emission line
properties of the sample and demonstrate that our high-redshift quasars do not
have unusual C\textrm{\textsc{IV}} line properties when compared to carefully
matched low-redshift samples. Our new DES+VHS $z>6.5$ quasars now add to the
growing census of luminous, rapidly accreting supermassive black-holes seen
well into the epoch of reionisation.
