Physical Properties of 15 Quasars at z ≳ 6.5

• Main Authors: Mazzucchelli, C. (Author), Bañados, E. (Author), Venemans, B. P. (Author), Decarli, R. (Author), Farina, E. P. (Author), Walter, F. (Author), Eilers, A.-C (Author), Rix, H.-W (Author), Fan, X. (Author), Rosa, G. De (Author), Hennawi, J. (Author), Chambers, K. C. (Author), Burgett, W. (Author), Draper, P. W. (Author), Kaiser, N. (Author), Kudritzki, R.-P (Author), Metcalfe, N. (Author), Wainscoat, R. J. (Author), Simcoe, Robert A (Contributor), Sternberg, David C. (Contributor), Schlafly, Eddie Ford (Contributor), Greiner, Julia (Contributor), Magnier, Eugene A. (Contributor), Waters, Christopher Lee (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Aeronautics and Astronautics (Contributor), Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences (Contributor), Massachusetts Institute of Technology. Department of Physics (Contributor)
• Format: Article
• Language: English
• Published: American Astronomical Society, 2018-08-28T14:52:34Z.
• Subjects: Article
• Online Access: Get fulltext

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 (<800Myr 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 CIVλ1549 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 (MBH∼(0.3-5) × 109M⊙) 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 〈(LbolLEdd)〉 = 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.
National Science Foundation (U.S.) (grant AST-9987045)
National Science Foundation (U.S.). Telescope System Instrumentation Program
Ohio Board of Regents
Ohio State University. Office of Research