DISCOVERY OF THREE z > 6.5 QUASARS IN THE VISTA KILO-DEGREE INFRARED GALAXY (VIKING) SURVEY

By B. Venemans, J. Findlay, W. Sutherland, G. D. Rosa, R. McMahon, R. Simcoe, E. González-Solares, K. Kuijken, J. S. M. Heidelberg, D. University and 7 more. 2013

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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(MBH > 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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/d46346d68d7a6e7370a38366c4cdc44a4729a476

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Citations in the corpus

The bright end of the galaxy luminosity function at z≃7: before the onset of mass quenching? (2013, methodology): “The strength of the evolution when extended to higher redshift is supported by Venemans et al. (2013) at z = 7 who found k = −0.49+0.28−0.74.”
SUBARU HIGH-z EXPLORATION OF LOW-LUMINOSITY QUASARS (SHELLQs). I. DISCOVERY OF 15 QUASARS AND BRIGHT GALAXIES AT 5.7 < z < 6.9 (2016, unknown): “With the advent of the Visible and Infrared Survey Telescope for Astronomy (VISTA) Kilo-degree Infrared Galaxy (VIKING) survey, more z > 6.5 quasars have been discovered in recent years (Venemans et al. 2013, 2015b).”
Pōniuā‘ena: A Luminous z = 7.5 Quasar Hosting a 1.5 Billion Solar Mass Black Hole (2020, background): “…in a sixfold increase in the number of known quasars at z > 6.5: 47 luminous quasars at z > 6.5 have been discovered (e.g., Fan et al. 2019; Venemans et al. 2013, 2015; Wang et al. 2019; Mazzucchelli et al. 2017; Reed et al. 2019; Matsuoka et al. 2019a; Yang et al. 2019), although among…”
Observational evidence for intermediate-mass black holes (2017, unknown): “Quasars with BH masses of up to 1010 M have been detected when the Universe was only 0.8 Gyr old (z ∼ 7, e.g., Fan et al. 2001, 2003; Willott et al. 2007, 2010; Mortlock et al. 2011; Venemans et al. 2013; Wu et al. 2015).”
The first and second data releases of the Kilo-Degree Survey (2015, methodology): “Adding the i-band KiDS data in the photometric selection removes ∼50% of these Z-band drop-out candidates (Venemans et al. 2013).”
Physical Properties of 15 Quasars at z ≳ 6.5 (2017, methodology): “…quasars have been discovered at such distance prior to the results presented here: three from the VISTA Kilo-Degree Infrared Galaxy Survey (VIKING; Venemans et al. 2013), four from PS1 (Venemans et al. 2015a, Tang et al. 2017), one from the Subaru Hyper Suprime-Cam-SPP Survey (HSC-SPP; Matsuoka…”
The bolometric quasar luminosity function at z = 0–7 (2020, background): “In the last decade, the redshift frontier of the observations of quasars have been pushed up to z > 7 (Mortlock et al. 2011; Bañados et al. 2018; Wang et al. 2018b) and about ∼ 50 quasars are now known at z ∼ 6 − 7 (e.g., Willott et al. 2010; Venemans et al. 2013, 2015; Jiang et al. 2016; Reed et al”
THE FINAL SDSS HIGH-REDSHIFT QUASAR SAMPLE OF 52 QUASARS AT z > 5.7 (2016, background): “5 7.4 in the near future (Venemans et al. 2013).”
Hyper-Eddington accretion flows on to massive black holes (2015, background): “The existence of bright quasars (QSOs) at highredshift (z & 6) provides a challenging puzzle about the origin of supermassive black holes (SMBHs) with masses & 109 M⊙ (Fan 2006; Willott et al. 2010; Mortlock et al. 2011; Venemans et al. 2013; Bañados et al. 2014; Wu et al. 2015).”
THE PAN-STARRS1 DISTANT z > 5.6 QUASAR SURVEY: MORE THAN 100 QUASARS WITHIN THE FIRST GYR OF THE UNIVERSE (2016, methodology): “−30◦ were discovered by Carnall et al. (2015), Reed et al. (2015), and Venemans et al. (2013, 2015a) using the VST ATLAS, DES, and VIKING and KiDS surveys, respectively.”
Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “Gunn-Peterson troughs that have been detected in the spectra of quasars z 6 (e.g. Becker et al. 2001; Fan et al. 2002; Mortlock et al. 2011; Venemans et al. 2013) suggest that the intergalactic medium (IGM) contained a significant neutral fraction (with a volume averaged fraction 〈xHI〉V ∼ 0.1, see…”
New constraints on lyman-α opacity with a sample of 62 quasars at z > 5.7 (2018, methodology): “…et al. 2016), the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS, Kaiser et al. 2010), the VISTA Kilo-Degree Infrared Galaxy (Venemans et al. 2013; Carnall et al. 2015) survey, the Canada–France High-redshift Quasar Survey (CFHQS; Willott et al. 2007), and UKIRT Infrared…”
BLACK HOLE MASS ESTIMATES AND EMISSION-LINE PROPERTIES OF A SAMPLE OF REDSHIFT z > 6.5 QUASARS (2013, methodology): “A detailed description of observing conditions and data reduction can be found in Venemans et al. (2013) for J0305–3150 and in Simcoe et al. (2012) for J1120+0641.”
Formation of Supermassive Black Hole Seeds (2016, background): “…a few billion solar masses within the 1 Gyr after the Big Bang (Fan et al. 2006; Willott et al. 2007; Jiang et al. 2008, 2009; Mortlock et al. 2011; Venemans et al. 2013; Bañados et al. 2014; Venemans et al. 2015; Jiang et al. 2015; Wu et al. 2015)1 How do they form and what are their formation…”
An ALMA [C ii] Survey of 27 Quasars at z > 5.94 (2018, unknown): “…quasars known in the literature at >z 5.5, 119 at >z 6.0, 15 at >z 6.5, and only two at >z 7.0 (see, e.g., Fan et al. 2006; Mortlock et al. 2011; Venemans et al. 2013; Bañados et al. 2016, 2018; Jiang et al. 2016; Matsuoka et al. 2016, 2017; Mazzucchelli et al. 2017; Wang et al. 2017, and…”