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http://hdl.handle.net/20.500.12386/29784
Titolo: | Physical Properties of 15 Quasars at z ≳ 6.5 | Autori: | Mazzucchelli, C. Banados, E. Venemans, Bram DECARLI, ROBERTO Farina, E.P. Walter, f. Eilers, A.-C. Rix, H.-W. Simcoe, R. Stern, D. Fan, X. Schlafly, E. De Rosa, G. 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. |
Data pubblicazione: | 2017 | Rivista: | THE ASTROPHYSICAL JOURNAL | 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. | URI: | http://hdl.handle.net/20.500.12386/29784 | URL: | https://iopscience.iop.org/article/10.3847/1538-4357/aa9185 | ISSN: | 0004-637X | DOI: | 10.3847/1538-4357/aa9185 | Bibcode ADS: | 2017ApJ...849...91M | Fulltext: | open |
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