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 AllSky 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 (JAB = 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 × 10M . Combining with the bolometric luminosities of these quasars of Lbol ' 1 3 × 10implies that the Eddington ratios are high '0.6-1.1. We consider the CIV emission line properties of the sample and demonstrate that our highredshift quasars do not have unusual CIV 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.