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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 693415.0, MPI für Astronomie / Publikationen_mpia
Discovery of three z > 6.5 quasars in the VISTA Kilo-Degree Infrared Galaxy (VIKING) Survey
Authors:Venemans, B. P.; Findlay, J. R.; Sutherland, W. J.; De Rosa, G.; McMahon, R. G.; Simcoe, R.; González-Solares, E. A.; Kuijken, K.; Lewis, J. R.
Date of Publication (YYYY-MM-DD):2013
Title of Journal:The Astrophysical Journal
Start Page:id. 24 (13 pp)
Audience:Not Specified
Abstract / Description:Studying quasars at the highest redshifts can constrain models of galaxy and black hole formation, and it also probes the intergalactic medium in the early universe. Optical surveys have to date discovered more than 60 quasars up to z ~= 6.4, a limit set by the use of the z-band and CCD detectors. Only one z >~ 6.4 quasar has been discovered, namely the z = 7.08 quasar ULAS J1120+0641, using near-infrared imaging. Here we report the discovery of three new z >~ 6.4 quasars in 332 deg2 of the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, thus extending the number from 1 to 4. The newly discovered quasars have redshifts of z = 6.60, 6.75, and 6.89. The absolute magnitudes are between –26.0 and –25.5, 0.6-1.1 mag fainter than ULAS J1120+0641. Near-infrared spectroscopy revealed the Mg II emission line in all three objects. The quasars are powered by black holes with masses of ~(1-2) × 109 M . In our probed redshift range of 6.44 < z < 7.44 we can set a lower limit on the space density of supermassive black holes of ρ(M BH > 109 M ) > 1.1 × 10–9 Mpc–3. The discovery of three quasars in our survey area is consistent with the z = 6 quasar luminosity function when extrapolated to z ~ 7. We do not find evidence for a steeper decline in the space density of quasars with increasing redshift from z = 6 to z = 7. Based on observations collected at the European Southern Observatory, Chile, programs 179.A-2004, 087.A-0717, 087.A-0890 and 088.A-0897. This paper also includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.
Free Keywords:cosmology: observations; galaxies: active; quasars: general; quasars: individual: VIKING J234833.34–305410.0 J010953.13–304726.3 J030516.92–315056
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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