Discovery of 16 New z ∼ 5.5 Quasars: Filling in the Redshift Gap of Quasar Color Selection

Yang, Jinyi; Fan, Xiaohui; Wu, Xue-Bing; Wang, Feige; Bian, Fuyan; Yang, Qian; McGreer, Ian D.; Yi, Weimin; Jiang, Linhua; Green, Richard; Yue, Minghao; Wang, Shu; Li, Zefeng; Ding, Jieqiong; Dye, S.; Lawrence, Andy

doi:10.3847/1538-3881/aa6577

Cited by 47 publications

(48 citation statements)

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“…We also include some quasars, which are not in the SDSS DR7 or DR12 catalog. A high redshift quasar catalog with 437 z > 4.5 (called the BONUS high redshift sample) was constructed from the literature (Table 1 and Table 3 in Wang et al (2015) and references therein; Table 7 in Bañados et al (2016) and references therein; Jiang et al 2016;Yang et al 2017;Wang et al 2017). …”

Section: Spectroscopically Identified Quasar Samplementioning

confidence: 99%

Quasar Photometric Redshifts and Candidate Selection: A New Algorithm Based on Optical and Mid-infrared Photometric Data

Yang

Fan

et al. 2017

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We present a new algorithm to estimate quasar photometric redshifts (photo-zs), by considering the asymmetries in the relative flux distributions of quasars. The relative flux models are built with multivariate Skew-t distributions in the multi-dimensional space of relative fluxes as a function of redshift and magnitude. For 151,392 quasars in the SDSS, we achieve a photo-z accuracy, defined as the fraction of quasars with the difference between the photo-z z p and the spectroscopic redshift z s , |∆z| = |z s − z p |/(1 + z s ) within 0.1, of 74%. Combining the WISE W1 and W2 infrared data with the SDSS data, the photo-z accuracy is enhanced to 87%. Using the Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-z accuracies are 79% and 72%, respectively. The prior probabilities as a function of magnitude for quasars, stars and galaxies are calculated respectively based on (1) the quasar luminosity function; (2) the Milky Way synthetic simulation with the Besançon model; (3) the Bayesian Galaxy Photometric Redshift estimation. The relative fluxes of stars are obtained with the Padova isochrones, and the relative fluxes of galaxies are modeled through galaxy templates. We test our classification method to select quasars using the DECaLS g, r, z, and WISE W1 and W2 photometry. The quasar selection completeness is higher than 70% for a wide redshift range 0.5 < z < 4.5, and a wide magnitude range 18 < r < 21.5 mag. Our photo-z regression and classification method has the potential to extend to future surveys. The photo-z code will be publicly available.

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Section: Spectroscopically Identified Quasar Samplementioning

confidence: 99%

Quasar Photometric Redshifts and Candidate Selection: A New Algorithm Based on Optical and Mid-infrared Photometric Data

Yang

Fan

et al. 2017

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“…The study of high-redshift active galactic nuclei (AGN) represents one of the frontiers of modern astrophysics. In the past decades, more than 200 quasars (QSOs) with spectroscopic redshift z > 5.5 were discovered by wide-area optical and near-IR (NIR) surveys (Fan et al 2006;Willott et al 2010;Venemans et al 2013;Bañados et al 2016Bañados et al , 2018Matsuoka et al 2016;Reed et al 2017;Tang et al 2017;Yang et al 2017).…”

Section: Introductionmentioning

confidence: 99%

The 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030 + 0524

Nanni¹,

Gilli²,

Vignali³

et al. 2018

A&A

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We present the results from a ~ 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030 + 0524. This is the deepest X-ray observation to date of a z ~ 6 QSO. The QSO is detected with a total of 125 net counts in the full (0.500A0–7 keV) band and its spectrum can be modeled by a single power-law model with photon index of Γ = 1.81 ± 0.18 and full band flux of f = 3.95 × 10−15 erg s−1 cm−2. When compared with the data obtained by XMM-Newton in 2003, our Chandra observation in 2017 shows a harder (ΔΓ ≈ −0.6) spectrum and a 2.5 times fainter flux. Such a variation, in a timespan of ~ 2 yr rest-frame, is unexpected for such a luminous QSO powered by a > 109M⨀ black hole. The observed source hardening and weakening could be related to an intrinsic variation in the accretion rate. However, the limited photon statistics does not allow us to discriminate between an intrinsic luminosity and spectral change, and an absorption event produced by an intervening gas cloud along the line of sight. We also report the discovery of diffuse X-ray emission that extends for 30″ × 20″ southward of the QSO with a signal-to-noise ratio (S/N) of approximately six, hardness ratio of HR = 0.03+0.20−0.25, and soft band flux of f0.5– keV = 1.1+0.3−0.3 × 10−15 erg s−1 cm−2 , that is not associated to a group or cluster of galaxies. We discuss two possible explanations for the extended emission, which may be either associated with the radio lobe of a nearby, foreground radio galaxy (at z ≈ 1 – 2), or ascribed to the feedback from the QSO itself acting on its surrounding environment, as proposed by simulations of early black hole formation.

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“…They represent a basic point of reference, providing the statistical samples needed to address many intrinsically large angular area problems in astronomy such as studying the structure of the Milky Way and investigating the global structure of the Universe. Large area surveys are also a source of unexpected and serendipitous discoveries of rare c 2017 The Authors and new classes of objects, such as high redshift quasars (see Wang et al 2017;Yang et al 2017), ultra-cool brown dwarfs and free-floating planets (see, for example Liu et al 2013;Marocco et al 2014). Full-sky or near full-sky survey coverage brings about the capability of retrospective identification of sources, for example, following a rare event or to find counterparts to sources detected at longer wavelengths where resolution is poor.…”

Section: Introductionmentioning

confidence: 99%

The UKIRT Hemisphere Survey: definition and J-band data release

Dye

Lawrence

Read

et al. 2017

Monthly Notices of the Royal Astronomical Society

136

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This paper defines the UK Infra-Red Telescope (UKIRT) Hemisphere Survey (UHS) and release of the remaining ∼12,700 deg 2 of J-band survey data products. The UHS will provide continuous J and K band coverage in the northern hemisphere from a declination of 0• to 60• by combining the existing Large Area Survey, Galactic Plane Survey and Galactic Clusters Survey conducted under the UKIRT Infra-red Deep Sky Survey (UKIDSS) programme with this new additional area not covered by UKIDSS. The released data includes J band imaging and source catalogues over the new area, which, together with UKIDSS, completes the J-band UHS coverage over the full ∼17,900 deg 2 area. 98 per cent of the data in this release have passed quality control criteria, the remaining 2 per cent being scheduled for re-observation. The median 5σ point source sensitivity of the released data is 19.6 mag (Vega). The median full width at half-maximum of the point spread function across the dataset is 0.75 arcsec. In this paper, we outline the survey management, data acquisition, processing and calibration, quality control and archiving as well as summarising the characteristics of the released data products. The data are initially available to a limited consortium with a world-wide release scheduled for August 2018.

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Discovery of 16 New z ∼ 5.5 Quasars: Filling in the Redshift Gap of Quasar Color Selection

Cited by 47 publications

References 45 publications

Quasar Photometric Redshifts and Candidate Selection: A New Algorithm Based on Optical and Mid-infrared Photometric Data

Quasar Photometric Redshifts and Candidate Selection: A New Algorithm Based on Optical and Mid-infrared Photometric Data

The 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030 + 0524

The UKIRT Hemisphere Survey: definition and J-band data release

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