Physical Properties of 15 Quasars at z ≳ 6.5

C. Mazzucchelli, E. Bañados, B. P. Venemans, R. Decarli, E. P. Farina, F. Walter, A. C. Eilers, H. W. Rix, R. Simcoe, D. Stern, X. Fan, E. Schlafly, G. De Rosa, J. Hennawi, K. C. Chambers, J. Greiner, W. Burgett, P. W. Draper, N. Kaiser, R. P. KudritzkiE. Magnier, N. Metcalfe, C. Waters, R. J. Wainscoat

Research output: Contribution to journalArticle

64 Scopus citations


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 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 (MBH ∼(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 〈(Lbol LEdd)〉 = 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.

Original languageEnglish (US)
Article number91
JournalAstrophysical Journal
Issue number2
StatePublished - Nov 10 2017



  • galaxies: high-redshift
  • quasars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Mazzucchelli, C., Bañados, E., Venemans, B. P., Decarli, R., 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., ... Wainscoat, R. J. (2017). Physical Properties of 15 Quasars at z ≳ 6.5. Astrophysical Journal, 849(2), [91].