Abstract
We report the results from a search for z > 6.5 quasars using the Dark Energy Survey (DES) Year 3 data set 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 - VDES J0244-5008 (z = 6.724), VDES J0020-3653 (z = 6.834), and VDES J0246-5219 (z = 6.90) - which were selected as the highest priority candidates in the survey data without any need for additional follow-up observations. We have obtained spectroscopic observations in the near-infrared for VDES J0244-5008 and VDES J0020-3653 as well as our previously identified quasar, VDES J0224-4711 at z = 6.50 from Reed et al. We use the near-infrared spectra to derive virial black holemasses from the full width at half-maximum of the MgII line. These black hole masses are ≃1-2 × 109M⊙. Combined with the bolometric luminosities of these quasars of Lbol ≃ 1-3 × 1047, these imply that the Eddington ratios are high, ≃0.6-1.1. We consider the C IV emission line properties of the sample and demonstrate that our highredshift quasars do not have unusual C 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 reionization.
Original language | English (US) |
---|---|
Pages (from-to) | 1874-1885 |
Number of pages | 12 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 487 |
Issue number | 2 |
DOIs | |
State | Published - Aug 1 2019 |
Keywords
- Dark ages, reionization, first stars
- Galaxies: active
- Galaxies: formation
- Galaxies: high-redshift
- Quasars: individual: VDES J0020-3653
- Quasars: individual: VDES J0224-4711
- Quasars: individual: VDES J0244-5008
- Quasars: individual: VDES J0246-5219
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science