Discovery of Eight z ~ 6 Quasars in the Sloan Digital Sky Survey Overlap Regions

Abstract

We present the discovery of eight quasars at z~6 identified in the Sloan Digital Sky Survey (SDSS) overlap regions. Individual SDSS imaging runs have some overlap with each other, leading to repeat observations over an area spanning >4000 deg^2 (more than 1/4 of the total footprint). These overlap regions provide a unique dataset that allows us to select high-redshift quasars more than 0.5 mag fainter in the z band than those found with the SDSS single-epoch data. Our quasar candidates were first selected as i-band dropout objects in the SDSS imaging database. We then carried out a series of follow-up observations in the optical and near-IR to improve photometry, remove contaminants, and identify quasars. The eight quasars reported here were discovered in a pilot study utilizing the overlap regions at high galactic latitude (|b|>30 deg). These quasars span a redshift range of 5.86<z<6.06 and a flux range of 19.3<z_AB<20.6 mag. Five of them are fainter than z_AB=20 mag, the typical magnitude limit of z~6 quasars used for the SDSS single-epoch images. In addition, we recover eight previously known quasars at z~6 that are located in the overlap regions. These results validate our procedure for selecting quasar candidates from the overlap regions and confirming them with follow-up observations, and provide guidance to a future systematic survey over all SDSS imaging regions with repeat observations.

arXiv commentAJ in press (8 pages)

References in corpus (44)

• The Sloan Digital Sky Survey: Technical Summary
• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Composite Quasar Spectra From the Sloan Digital Sky Survey
• The Sloan Digital Sky Survey Photometric Camera
• A luminous quasar at a redshift of z = 7.085
• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• A Survey of z>5.8 Quasars in the Sloan Digital Sky Survey I: Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z~6
• A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey II: Discovery of Three Additional Quasars at z>6
• A photometricity and extinction monitor at the Apache Point Observatory
• The Canada-France High-z Quasar Survey: nine new quasars and the luminosity function at redshift 6
• A Modified Magnitude System that Produces Well-Behaved Magnitudes, Colors, and Errors Even for Low Signal-to-Noise Ratio Measurements
• A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey IV: Discovery of Seven Additional Quasars
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• Star Formation and Gas Kinematics of Quasar Host Galaxies at z~6: New insights from ALMA
• A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey III: Discovery of Five Additional Quasars
• Clustering of High Redshift ($z\ge 2.9$) Quasars from the Sloan Digital Sky Survey
• A Description of Quasar Variability Measured Using Repeated SDSS and POSS Imaging
• Discovery of three z>6.5 quasars in the VISTA Kilo-degree Infrared Galaxy (VIKING) survey
• The Discovery of a Luminous z=5.80 Quasar from the Sloan Digital Sky Survey
• Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey
• A Kiloparsec-Scale Hyper-Starburst in a Quasar Host Less than 1 Gigayear after the Big Bang
• Gemini Near-infrared Spectroscopy of Luminous z~6 Quasars: Chemical Abundances, Black Hole Masses, and MgII Absorption
• Black hole masses and enrichment of z ~ 6 SDSS quasars
• Evidence for non-evolving FeII/MgII ratios in rapidly accreting z~6 QSOs
• The UKIRT Infrared Deep Sky Survey First Data Release
• The SDSS Coadd: 275 deg^2 of Deep SDSS Imaging on Stripe 82
• A Survey of z~6 Quasars in the SDSS Deep Stripe: I. a Flux-Limited Sample at z_{AB}<21
• A Survey of z~6 Quasars in the SDSS Deep Stripe. II. Discovery of Six Quasars at z_{AB}>21
• The identification of z-dropouts in Pan-STARRS1: three quasars at 6.5<z<6.7
• Discovery of eight z ~ 6 quasars from Pan-STARRS1
• Six more quasars at redshift 6 discovered by the Canada-France High-z Quasar Survey
• Ionization near-zones associated with quasars at z ~ 6
• SDSS quasars in the WISE preliminary data release and quasar candidate selection with optical/infrared colors
• Dust-free quasars in the early Universe
• Far-infrared and Molecular CO Emission From the Host Galaxies of Faint Quasars at z~6
• The Sloan Digital Sky Survey Stripe 82 Imaging Data: Depth-Optimized Co-adds Over 300 Deg^2 in Five Filters
• The first (nearly) model-independent constraint on the neutral hydrogen fraction at z~5--6
• The discovery of the first luminous z~6 quasar in the UKIDSS Large Area Survey
• Discovery of a redshift 6.13 quasar in the UKIRT Infrared Deep Sky Survey
• Probabilistic selection of high-redshift quasars
• The First High Redshift Quasar from Pan-STARRS
• First results from the Canada-France High-z Quasar Survey: Constraints on the z=6 quasar luminosity function and the quasar contribution to reionization
• Discovery of a new high redshift QSO at z=5.96 with the Subaru telescope

Cited by in corpus (52)

• The Pan-STARRS1 distant z>5.6 quasar survey: more than 100 quasars within the first Gyr of the universe
• The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7
• Hydrogen reionisation ends by $z=5.3$: Lyman-$\alpha$ optical depth measured by the XQR-30 sample
• Subaru high-z exploration of low-luminosity quasars (SHELLQs). I. Discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9
• Gemini GNIRS near-infrared spectroscopy of 50 quasars at z>~5.7
• Formation of supermassive black hole seeds
• EIGER I. a large sample of [OIII]-emitting galaxies at $5.3<z<6.9$ and direct evidence for local reionization by galaxies
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 Quasars and Luminous Galaxies at 5.7 < z < 6.8
• The compact, ~1 kpc host galaxy of a quasar at z=7.1
• The X-shooter/ALMA Sample of Quasars in the Epoch of Reionization. II. Black Hole Masses, Eddington Ratios, and the Formation of the First Quasars
• The X-SHOOTER/ALMA sample of Quasars in the Epoch of Reionization. I. NIR spectral modeling, iron enrichment and broad emission line properties
• EIGER V. Characterizing the Host Galaxies of Luminous Quasars at $z\gtrsim 6$
• A survey of luminous high-redshift quasars with SDSS and WISE. I. target selection and optical spectroscopy
• Probing the interstellar medium and star formation of the Most Luminous Quasar at z=6.3
• First discoveries of z~6 quasars with the Kilo Degree Survey and VISTA Kilo-Degree Infrared Galaxy survey
• First Discoveries of z>6 Quasars with the DECam Legacy Survey and UKIRT Hemisphere Survey
• Application of Stochastic Modeling to Analysis of Photometric Reverberation Mapping Data
• On the formation of the first quasars
• XQR-30: the ultimate XSHOOTER quasar sample at the reionization epoch
• Widespread, strong outflows in XQR-30 quasars at the Reionisation epoch
• Co-evolution of massive black holes and their host galaxies at high redshift: discrepancies from six cosmological simulations and the key role of JWST
• Gas dynamics of a luminous $z$ = 6.13 quasar ULAS J1319$+$0950 revealed by ALMA high resolution observations
• Heavy Element Absorption Systems at $5.0<z<6.8$: Metal-Poor Neutral Gas and a Diminishing Signature of Highly Ionized Circumgalactic Matter
• A New Method to Measure the Post-Reionization Ionizing Background from the Joint Distribution of Lyman-$\alpha$ and Lyman-$\beta$ Forest Transmission
• XQR-30: Black Hole Masses and Accretion Rates of 42 z>6 Quasars
• A comparison of quasar emission reconstruction techniques for $z\ge 5.0$ Lyman-$\alpha$ and Lyman-$\beta$ transmission
• Constraining the quasar radio-loud fraction at $z\sim 6$ with deep radio observations
• Star Formation and ISM Properties in Host Galaxies of Three Far-infrared Luminous Quasars at $z\sim 6$
• Cosmic Reionization On Computers. Properties of the Post-reionization IGM
• The first Super Massive Black Holes: indications from models for future observations
• The Pan-STARRS1 $\mathbf{z}>5.6$ Quasar Survey: III. The $\mathbf{z}\approx 6$ Quasar Luminosity Function
• A new bright z=6.82 quasar discovered with VISTA: VHS J0411-0907
• The Near and Mid-infrared photometric properties of known redshift $z\ge 5$ Quasars
• A spectral stacking analysis to search for faint outflow signatures in z~6 quasars
• No Evidence for Millimeter Continuum Source Overdensities in the Environments of $z\gtrsim 6$ Quasars
• J0906+6930: a radio-loud quasar in the early Universe
• Discovery of the most X-ray luminous quasar SRGE J170245.3+130104 at redshift z$\approx 5.5$
• Demographics of z ~ 6 Quasars in the Black Hole Mass-Luminosity Plane
• Spectral Energy Distributions of Companion Galaxies to z$\sim$6 Quasars
• Quasars as probes of cosmological reionization
• Enhanced star formation in $z\sim 6$ quasar companions
• SCUBA2 High Redshift Bright Quasar Survey: Far-infrared Properties and Weak-line Features
• Milli-arcsecond imaging of the radio emission from the quasar with the most massive black hole at reionization
• Exploratory Chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30
• Reverberation Mapping with Intermediate-Band Photometry: Detection of Broad-Line H$\alpha$ Time Lags for Quasars at $0.2<z<0.4$
• Observations by GMRT at 323 MHz of radio-loud quasars at $z>5$
• The Infrared Medium-deep Survey. III. Survey of Luminous Quasars at 4.7 $\le$ z $\le$ 5.4
• Quasar UV Luminosity Function at $3.5<z<5.0$ from SDSS Deep Imaging Data
• The Infrared Medium-deep Survey. IX. Discovery of Two New $z\sim 6$ Quasars and Space Density down to $M_{1450}\sim -23.5$ mag
• An Optically Faint Quasar Survey at z~5 in the CFHTLS Wide Field: Estimates of the Black Hole Masses and Eddington Ratios
• Growth problems of stellar black holes in early galaxies
• The feedback of quasars on their galactic environment