Physical Properties of 15 Quasars at z ≳ 6.5

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.; Rosa, G. De; 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 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 CIV 1549\AAemission 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 MgII 2798\AAemission line and rest-frame UV continuum; we 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 FeII/MgII abundance ratio with cosmic time; (4) we derive near zone sizes; together with measurements for z∼6 quasars from recent work, we confirm a shallow evolution of the decreasing quasar near zone sizes with redshift. Finally, we present new millimeter observations of the [CII] 158 μm emission line and underlying dust continuum from NOEMA for four quasars, and provide new accurate redshifts and [CII]/infrared luminosities estimates. The analysis presented here shows the large range of properties of the most distant quasars.

Citation

Mazzucchelli, C., Bañados, E., Venemans, B., Decarli, R., Farina, E., Walter, F., …Wainscoat, R. (2017). Physical Properties of 15 Quasars at z ≳ 6.5. Astrophysical Journal, 849(2), Article 91. https://doi.org/10.3847/1538-4357/aa9185

• Journal Article Type: Article
• Acceptance Date: Oct 2, 2017
• Online Publication Date: Nov 6, 2017
• Publication Date: Nov 6, 2017
• Deposit Date: Nov 29, 2017
• Publicly Available Date: Nov 29, 2017
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 849
• Issue: 2
• Article Number: 91
• DOI: https://doi.org/10.3847/1538-4357/aa9185
• Public URL: https://durham-repository.worktribe.com/output/1343035