Physical Properties of 15 Quasars at z ≳ 6.5
Journal
Date Issued
2017
Author(s)
Mazzucchelli, C.
•
Banados, E.
•
Venemans, Bram
•
•
Farina, E.P.
•
Walter, f.
•
Eilers, A.-C.
•
Rix, H.-W.
•
Simcoe, R.
•
Stern, D.
•
Fan, X.
•
Schlafly, E.
•
•
Hennawi, J.
•
Chambers, K.C.
•
Greiner, J.
•
Burgett, W.
•
Draper, P.W.
•
Kaiser, N.
•
Kudritzki, R.-P.
•
Magnier, E.
•
Metcalfe, N.
•
Waters, C.
•
Wainscoat, R.J.
Abstract
Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only a few quasars have been reported at z> 6.5 (<800 Myr after the big bang). In this work, we present six additional z≳ 6.5 quasars discovered using the Pan-STARRS1 survey. We use a sample of 15 z≳ 6.5 quasars to perform a homogeneous and comprehensive analysis of this highest-redshift quasar population. We report four main results: (1) the majority of z≳ 6.5 quasars show large blueshifts of the broad C IV λ1549 emission line compared to the systemic redshift of the quasars, with a median value ∼3× higher than a quasar sample at z∼ 1; (2) we estimate the quasars’ black hole masses ({M}{BH} ∼ (0.3-5) × 109 M ☉) via modeling of the Mg II λ2798 emission line and rest-frame UV continuum and find that quasars at high redshift accrete their material (with < ({L}{bol}/{L}{Edd})> =0.39) at a rate comparable to a luminosity-matched sample at lower redshift, albeit with significant scatter (0.4 dex); (3) we recover no evolution of the Fe II/Mg II abundance ratio with cosmic time; and (4) we derive near-zone sizes and, together with measurements for z∼ 6 quasars from recent work, confirm a shallow evolution of the decreasing quasar near-zone sizes with redshift. Finally, we present new millimeter observations of the [C II] 158 μm emission line and underlying dust continuum from NOEMA for four quasars and provide new accurate redshifts and [C II]/infrared luminosity estimates. The analysis presented here shows the large range of properties of the most distant quasars.
Issn Identifier
0004-637X
Ads BibCode
2017ApJ...849...91M
Rights
open.access
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